1 deck. Easy. 1 redeal.
Duchess Solitaire uses 52 cards (1 deck). 12 cards are dealt to 4 reserve piles of 3 cards each. The next 4 open cards are tableau piles. 4 foundation piles are placed above. To start the game you have to choose the rank of your foundations. To do this just select the top card of any reserve pile and place it on any foundation. The 3 other cards of the same rank are moved to the foundations as they become available.
You may build tableaus down in sequence and alternating color. Only the top card of each tableau pile and the reserve piles is available for play on the foundations. One card or group of cards in the proper sequence can be moved to another tableau pile. When one of the tableaus is empty it may be filled up with a card from any reserve pile if possible, then by any card.
You have one redeal.