Here's another flat sinnet from Stuart Grainger's Creative Ropecraft. It's just one of many shown to be made with up to six strands in the book, like a previous one I blogged about a few years ago.
I've started this paracord belt version, using the buckle from an old leather belt. I've treated the pair of tan paracord lines as one cord. The tan and one of the foliage green paracord cords are strictly core strands for the sinnet to be woven around, and would only need to be as long at the belt would be, where the working strands(3 of them) would need to be much longer. I haven't figured out a needed length, feet of cord per inch of sinnet, because there are variables that would depend on how tight/loose the sinnet is made, size/number of core strands woven around, etc... The sinnet would also work well for a bracelet, pet collar, or strap.