I liked the INGOLF counter height stool, but too hard. I tried the tie on cushions and they moved too much. So I decided to buy foam and faux leather.
Since the chair was already apart in the box, we assembled everything but the seat. The leather was going to take up some space, so we used a jigsaw to make the notch in the back of the seat 1/4 inch bigger.
Then I cut the foam using electric knife to size.
Cut the leather 4 inches wider on all sides. Then used a power stapler and stretch the leather around the seat and tacked it in place.
You can stop there, but I went a little further in my design and added cording using the same faux leather. We tacked it on using the same power stapler.