directed from: Shop Machines The Flask Booth is a structure found in the Spell Shop that sells an infinite amount of flasks to the player for 35 shillings each.
When the player enters the Spell Shop, theres a 35% chance that the Flask Booth will spawn in next to the Master of Shopkeeping NPC. This chance can be increased depending on the player's Luck statistic in their current run.
The Flask Booth rolls from a separate special loottable instead of the basic flask loottable. This contains a few extra magical flasks which can benefit the player more than just the basic flasks.