Look at the knots that are used to finish off laid rope. Crown, wall etc and the variants and compounds thereof. Most instructions you'll find are for three strands, but as the knots are symmetric, the tying method can be extended to as many strands as you want. I often use a doubled diamond knot to anchor my braids - if you want, you can leave the loose ends as a tassle, or cut them off flush.

Willeke has some good info on her site, and the bible would be "Ashley's Book of Knots" if you can find a copy in your library (most seem to have them).

Some more discussion in:

This Knot Thread

Matthias

The easiest way to think about converting from three to four strands is to forget about the knot as a whole and just look at what one strand does. For example, the "basic" pattern might be "under one, over one" repeated with each strand. If you have instructions for a 3 strand knot, and you have 4 or more, practice the three strand version first!

A BIG help when trying to learn new knots is to start with really large cord/rope so you can see what is going on. See if you can find some 1/4 inch or larger material to test with. Braid a section the way you are planning to, and then try out the knots.

I find with a lot of these types of knots that it is easier to handle if I make sure to arrange the strands in an organised way rather than try to freehand them. If you look at

the diagram taken from ABOK

you can see that he's use a tie to keep the loops in place. It also makes it much easier to see what is meant to happen, rather than just blindly copying crossings.

Hope you figure it out! Stylish way to finish off a braid...

Matthias