Measure space and subtract 1" from all four sides to get your final measurements. 2. Cut plywood per your final measurements. 3. Cut upholstery foam per your final measurements. 4. Place your fabric, foam, and plywood straight on a flat surface. 5. Cut fabric 7" to 8" longer than all four sides. 6. Wrap and staple your fabric. 8. Place your DIY window seat cushion and enjoy!