Stronghold is a small set with 55 commons, 44 uncommons, and 44 rares. This is a new size for small sets, smaller than Visions and Weatherlight. The set was printed in the USA and Belgium. 
Stronghold was sold in 15 card booster packs. Booster boxes have 36 packs.
The Belgian printing uses striped collation with 10 × 11 sheets and 12 × 11 sheets. Packs are back-facing and contain 3 uncommons, 1 rare, and 11 commons (in that order).
|3 Uncommons||1 Rare||11 Commons|
The use of 12 × 11 sheets to print uncommons (and probably rares) has been confirmed by reconstructing uncommon sheets from sets with 44 uncommons including this one and the one from Nemesis. (Note that US printings with sequential collation don't seem to use 12 × 11 sheets in this way, though.)
The common sheet contains 55 cards each twice. The choice of top row prevents blue cards from showing up next to each other on the sheet.
The uncommon sheet contains 44 cards each three times. Note that the Corrupting Licid and Flowstone Hellion in the top row were not observed, so their positions are a guess. (I guessed that each column would have a monocolor card of every color.) Also, the choice of top row here is mostly arbitrary.
 The "Compilation of Manufacture Information for MTG Products" thread on the Magic Librarities Forum confirms the existence of US-printed Stronghold, but I couldn't identify any US openings during my research.