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hello i have a circle kumihimo board but was wondering if anyone has used a square one before and if so can i used similar patterns or not

The shape of the disc doesn’t make any difference on what kind of kumihimo you can make with it. It’s the movement of the strings that form the kumihimo. Traditionally any kumihimo was made on a round stool (marudai) or on a big weaving stand (takadai).
So it’s only the placements of the slits that can be more to your liking, but you never really need a square disc. The only exception I can think of is when the flat kumihimo you are making is wider than the hole in your disc.

I've seen where people use round kumihimo wheels, they produce braided cords, you know like the kumi bracelets we've all seen before. With a square kumihimo wheel, you can make flat braids with it and they can turn out pretty different. There's quite a few tutorials with both shaped discs on YouTube!