How To Make Martial Art Belt

There are 2 martial art belt models, Japanese (Obi) and Chinese (Dai):

By the way, we don’t need buying overpriced belt sold at expensive stores. We can make it by ourselves using cheap cloth at home (ancient warriors also using normal - daily cloth back then).

Based on my bad experience, overpriced martial art belts made thicker with additional wide hard sponge or rubber strap inside without logic reason (maybe to make it look cooler or look expensive?). Those expensive - hard belts knot are always opened itself during training, we could never tie them tightly because those rubber belts are too thick, very very annoying.