Find a pair of floor pillows that you like and measure them. Ideally they should be square and able to stack one on top of the other. Box-edged floor cushions are perfect for this job, but you can use any other floor cushion or sofa cushion that you find.
Have a piece of wood cut to the same size as the pillows at your local hardware or home improvement store. You will paint the wood, so any type of wood will work. Regular plywood is perfect for this job.
Paint the wood with latex paint using a smooth foam roller. Apply two coats of paint, allowing the paint to dry completely between coats.
Apply polyurethane to the painted wood. Padded footstools get a lot of wear and tear. The polyurethane will protect the finish of the paint and prevent chipping. Polyurethane comes in matte and glossy finish. Either type will provide the same protection. Choose whichever finished look you prefer. Allow polyurethane to dry completely.
Place your casters on what will be the bottom of the padded footstool. Casters should sit approximately 2 inches from the corners of the wood. Mark the holes in the casters with a pencil. Drill holes at your pencil marks. Screw the casters in place.
Turn the footstool over so that the casters are on the ground. Attach self-adhesive Velcro in multiple spots on the wood. Attach the corresponding Velcro to the bottom of the cushion. Add more Velcro between the two cushions to prevent slipping. Stack cushions on top of one another on your wooden platform to complete your padded footstool.