Step 1: Draw and cut arches. After determining your size and layout, first cut the vertical strips of plywood. ... Step 2: Trace and cut drywall. ... Step 3: Attach plywood to the wall. ... Step 4: Attach drywall onto the plywood. ... Step 5: Mud and tape drywall seams. ... Step 6: Add corner bead. ... Step 7: Sand and (optional) skim coat.