Open slow cooker liner and place it inside the slow cooker bowl. Fit liner snugly against the bottom and sides of bowl; pull top of liner over rim of bowl.

Place water and three-fourths of the vegetables in the lined-slow cooker. Reserve 1 Tbsp onion soup mix. Sprinkle remaining onion soup mix over vegetables; stir gently to coat evenly. Sprinkle and rub salt, pepper and theme over the pot roast. Place pot roast on top of vegetables. Place remaining vegetables around pot roast; sprinkle vegetables with remaining onion soup mix. Place lid on slow cooker.

Cook on low for 8 to 9 hours or on high for 5 to 6 hours, until pot roast is tender.

Carefully remove lid to allow steam to escape. Serve food directly from lined-slow cooker. Do not lift or transport liner with food inside. Cool slow cooker completely; remove liner and toss.