I make these straps for small lap harps. They've been put on 22 to 26 string harps - the harp in the smaller pictures is a Stoney End Brittany. The larger harp above is a Stoney End Anne. I'm doing a very slight modification to the bottom of the strap, so it will work equally well for both left and right side players. I'll put the plans up here someday, so you can make your own.

It's easy to attach - at the top of the harp, I use two thongs here because if, Goddess forbid, there were only one and it broke...
At the other end, the holes are at a 45 degree slant, so that when tied on, the strap is at an angle to the base and will pass around the left side of your body. I tie the bottom thong around the pillar, but not dead tight so I can slide it up the pillar to take up all the slack in the strap and put it in the case for transporting. If you wish, you can use two thongs here, but it really isn't as necessary, as most of the weight hangs from the top.

I just "put it on" like an electric guitar. The strap goes over my right shoulder, across my back diagonally and around my left side. You can play while walking around, which is kind of fun. I do the "wandering minstrel" thing at SCA events, it's perfect for that...