Seeding method for 1 pack:

1. Add 1 Cryptic Spires from outside the cube

2. Randomly make 3 piles of 1 common at WUBRG and 2 multicolor (7 cards each pile). Add 1 pile and 1 card from the second pile randomly to the pack (8 commons in pack). Add the remainder of the second pile and the third pile to the "foil" slot pile. (13 commons in pile)

3. Get 1 of each WUBRG uncommon, 3 multicolour uncommons and 1 colourless uncommon (9 cards). Select 3 random cards and add to the pack (3 uncommons in pack), then add the remainder to the "foil" slot pile (6 uncommons in pile).

4. Get 3 random rares/mythics and select 2 (2 rares in pack). Add the last one to the "foil" slot pile (1 rare in pile).

5. The "foil" slot pile should have 20 cards (1 R 6 UC 13 C). Select 2 randomly and add to the pack. Outcomes and probability:

Rare + common: 13/190, ~6.8%
Rare + uncommon: 6/190, ~3.2%
2 uncommons: 15/190, ~7.9%
uncommon + common: 78/190 ~41.1%
2 commons: 78/190 ~41.1%

Return the remainder of the "foil" pile to the cube (or repurpose the remainder into the next pack seed)

1. Your final pack should have:
   1 Cryptic Spires
   8 Commons, 1 of each WUBRG, 2 multicoloured, 1 random
   3 Uncommons, random
   2 Rares, random
   2 "foils", any rarity

Total: 16 cards

Happy cubing!

Exclusions:
Reasons - poor synergy, or simply just not in my possession
Shadowborn Apostle
Summer Bloom
Wrenn and Six
Imperial Seal
Dockside Extortionist
Mana Vault
Phyrexian Altar
Crucible of Worlds
The Eldrazis
Smothering Tithe
Teferi's Protection
Weathered Wayfarer
As Foretold
Force of Negation
Mana Drain
Surgical Extraction
Chaos Warp
Warrior's Oath
Bloom Tender
Concordant Crossroads
Food Chain
Atla Palani
Doran, the Siege Tower
Guided Passage
Jodah
Kaalia
Master of Cruelties
Thousand-Year Storm
Zur the Enchanter
Aether Vial
Sensei's Divining Top
Thrumming Stone
Vedalken Orrery
Cavern of Souls
Forbidden Orchard
Pillar of the Paruns