Remove the staples from the cambric
underneath the stool, fold it back, and then remove all of the seat fabric and foam. Replace with new foam and fabric, then lay the cambric back in place and staple it down.
If the cambric is too far gone too, then just remove it altogether and add a new piece when the seat is done and just staple and trim it neatly right up against the base.
You need a special tool to get the special washer off before you can take the seat off the stem, and I think it's easier and safer not to mess with that. You aren't permanently altering the stool if you do it the way I suggested. But if you want to do it 100% like the original, you have to get that washer off.
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