Steps 3-5: Cut the pant legs leaving enough excess to fold over cushion. Cut the inseam of each pant leg, remove the unneeded front of the pants, fold the top of the leg over and use fabric leftovers to fill in the triangle below, sewing all the edges down. Lay your cushion on the fabric panel you've just created and fold the pants over the edge and staple in place.
Step 6: Place the cushion back on the chair frame and screw together!