I would say the best knot for braiding paraxcord is the Slatt's Rescue belt knot
Slatt's Knot While the belt is great [and I'm wearing one as I type this] Don't limit yourself with the idea the only thing is a belt. The width is only limited to where you want to stop. What about a square or rectangular mat that will just fit a hip pocket. Nice padding. Maybe a pot holder sized one. Works as one in addition to lifting hot pots a ready supply of cordage.
The Knot works great with 550 cord but can work with any size cordage. Think lighter stuff to make a decorative hat band. Climbuing rope could be made into a sleeping mat. The list is endless. Use your imagination.