Baking and cutting eucharistic bread in the Eastern Orthodox Churches

Prolegomenon

There is an assumption that needs to be addressed before an answer can be given, namely that 'scripture' is the basis for practices and beliefs in the Eastern Orthodox Church. It is not. Scripture is a part of Holy Tradition (the preeminent portion indeed), but not everything comes from this. Most important is maintaining and passing on the Apostolic Tradition unaltered. So asking for a 'scriptural basis' for an Eastern Orthodox practice doesn't really make sense. It's sort of like asking for a Protestant justification of a Roman Catholic practice—you're using the wrong measuring stick for this context. With that said, I will proceed explaining the historical emergence of this practice.

The (Leavened) Bread

History shows that using leavened bread is the earliest practice of the Christian Church. The use of unleavened bread is a later development (8th or 9th century, depending on which scholar you cite):

In the West, various ordinances appeared from the ninth century on, all demanding the exclusive use of unleavened bread for the Eucharist. A growing solicitude for the Blessed Sacrament and a desire to employ only the best and whitest bread, along with various scriptural considerations—all favored this development. Still, the new custom did not come into exclusive vogue until the middle of the eleventh century. Particularly in Rome it was not universally accepted till after the general infiltration of various usages from the North. In the Orient there were few objections to this usage during olden times. Not till the discussions that led to the schism of 1054 did it become one of the chief objections against the Latins. At the Council of Florence (1439), however, it was definitely established that the Sacrament could be confected in azymo sive fermentato pane. Therefore, as we well know, the various groups of Orientals who are united with Rome continue to use the type of bread traditional among them.¹

The use of unleavened bread is partly due to the assumption that the Last Supper occurred during the Passover Seder (and numerous anachronistic assumptions about how this meal was practiced in first century Judaism). This assumption is problematic from a historical perspective, however, because John's Gospel presents a different timeline than the Synoptic Gospels for this meal.²

The same baking method and ovens were used by the Christians for both their daily bread and that which was to be used in worship. It must be made clear that (contrary to practices today in the West) in the Early Christian centuries and in all eastern rites through the ages, except in the Armenian church, the bread used for the Church did not differ from ordinary bread in substance. From the beginning leavened bread was used. Even the Armenians before the seventh century and the Maronites before their union with Rome in the twelfth century used leavened bread. The practice of using unleavened bread for the Eucharist was introduced to the West much later. Among the earliest written accounts is that given by Alcuin (A.D. 798) and his disciple Rabanus Maurus. After this the altar bread took the light, wafer like form, achieved with pressing irons, so common today.³

Officially, according to the OCA,

In the Christian East there is no concern for using the exact type of bread used at the Last Supper....

Even so, you will hear some Orthodox Christians refer to unleavened bread as 'dead bread' in a derogatory fashion, and some elaborate allegorical theologies were developed by the eleventh century in the East that commingled the theology of the bread used in the Mystical Supper with that of Christology (e.g. as the body without breath and soul is dead, so also is unleavened bread; Christ gave us a whole loaf, not just his body without a soul as Apollinaris claims, etc.).

The Eastern Orthodox Church continues to follow the earliest Christian practice which we believe was handed down from the apostles: the use of leavened bread.

Breaking vs. Cutting the Bread

This distinction is somewhat semantic and anachronistic (they probably didn't cut bread with knives in first century Judea). The phrase 'break(ing) the bread' (τῇ κλάσει τοῦ ἄρτου, κλῶντές/κλάσαι/κλάσας τὸν ἄρτον, etc.) appears numerous times in the New Testament,⁴ and simply refers to 'breaking' or 'fracturing'.⁵ Due to the anachronistic nature of this question I will comment no further.

Who Gets to Bake It?

The idea of it being baked by someone 'in good standing' is because it is viewed as an honor to serve in this way, and the bread is an offering (πρόσφορον, prosphoron) at the altar (cf. Matthew 5:23-24 and note that the Orthodox refer to the bread with the same Greek term used in this passage).

In What Jurisdictions Does This Practice Occur?

This practice is used virtually unanimously in all Eastern Orthodox churches, with the notable exception of the Oriental Orthodox Armenian Apostolic Church. As I've pointed out elsewhere,

Concerning Eastern Orthodox and Oriental Orthodox Christians, the difference is that the latter accept only the first three ecumenical councils (Nicaea I, Ephesus I & Chalcedon), while the former accept seven ecumenical councils. There are some Eastern Orthodox Christians who consider the controversy between Oriental Orthodox and themselves to be primarily semantic (and some dialogue has been made in the 20th century to reunite the churches, but full communion has not yet been restored), but officially they are not considered to be 'Orthodox' (despite their use of the title) as they were condemned as heretical for rejecting the fourth ecumenical council (Chalcedon).

Conclusion

I've explained the historical emergence of the Eastern Orthodox practices mentioned in the question (they are the earliest known practice in the Christian Church), and I've addressed some of the faulty underlying assumptions in the question as well.

_{¹ Joseph A. Jungmann, The Mass Of The Roman Rite: Its Origins and Development, vol. 2. (Dublin, Ireland: Four Courts Press, 1986), 34.}

_{² cf. Jonathan Klawans, "Was Jesus’ Last Supper a Seder?" In Biblical Archaeology Review, Oct 2001, 24-33, 47.}

_{³George Galavaris, "Bread and the Liturgy: The Symbolism of Early Christian and Byzantine Bread Stamps". In Speculum Vol. 46, No. 1 (Jan, 1971), 154. DOI link.}

_{⁴ cf. Luke 24:35; Acts 2:42, 46; 20:7, 11; 27:35.}

_{⁵ William Arndt, Frederick W. Danker, and Walter Bauer, A Greek-English Lexicon of the New Testament and Other Early Christian Literature (Chicago: University of Chicago Press, 2000), 546-7. It is also noted that the use of this verb with the referent ἄρτος (bread) does not refer to cultic practices with any certainty (i.e. Eucharist/Communion/Mystical Supper or other cultic meals).}