Twenty reserve cards wait behind a single exposed card. Five tableau columns give you room to release them, while eight foundations build from ace to king.
The reserve claims empty columns
Build down in alternating colors. Exposed cards and ordered alternating-color runs can move together. When a column empties, its next card comes automatically from the reserve. Only after that reserve is gone can any card or legal run occupy the space.
Three passes through the larger stock
Two decks leave 79 cards in the draw-one stock after the reserve and opening tableau. You get three total passes, including the first. Look at the reserve card before drawing: finding its receiver may reveal another useful card immediately. Clearing the reserve is only part of the task; all 104 cards must reach the ace-based foundations.