Remove the seat from the frame using the appropriate screwdriver. Most fixed seat chairs and stools are relatively easy to disassemble. Just flip it upside down and remove all the screws to free the seat from its base.
Use the end of a flat tipped screwdriver to remove the staples holding the fabric to the seat. When the fabric is removed you will be left with a wooden base and a piece of upholstery foam that are the correct size of the item you are recovering. Use this base to help you make your template.
Place the wood base on top of a piece of cardboard or pattern paper. Measure the height of the piece of foam and board and add this measurement around the entire perimeter to accommodate for the height of the base. Trace out the shape on your piece of cardboard with a pencil or marker.
Use a pair of scissors to cut out your template. Use this template to help you cut out the fabric required to upholster your piece of furniture.