Remove the bindings from the ski with the screwdriver and discard the bindings. For this project, you only want the flat skis.
Determine the center point of each ski and mark this with a pencil.
Measure 12 inches from either side of the center of the ski and drill a hole with the drill bit. When you're done, each ski should have a hole several inches from either end, depending on the length of your skis.
Attach one of the pieces of 2-by-4 to two of the 4-by-4 pieces with 2-inch-long flat-head screws; use two screws at each end of the 2-by-4. Repeat with the other pieces of lumber. The 4-by-4s serve as legs for your bench and the 2-by-4 bridges the top of them. You should end up with two sections, each shaped like an upside-down U with the 2-by-4 at the top.
Set the leg sections you've just made on the ground, 24 inches apart. Arrange the skis across the two sections to form the seat of your bench. Space the skis approximately 1/2 inch apart to allow for drainage. Each end of the skis will extend over each side of the "legs" of the bench. When you're satisfied with the arrangement of the skis, attach the skis to the 2-by-4s with the 1 1/2-inch screws.