I have tried, Xanthan Gum, and Salt.
Xanthan Gum will seperate and it only absorbs what (straight water) is available in the solution, and the rest will settle on the bottom of the solution as a layer of sediment. So you need a lot of water in your solution for it to actually gel, if you make a gel first with water and add it to the soap solution, then it will seperate. But a pro is that if clarity or transparency is a goal, then Xanthan Gum is a hard but good choice. I have been very disappointed in Xanthan Gum after all the good things I read.
Salt works good if your soap solution is the proper dilution, over or under a certain point will cause it to seperateas well.
Recently I have just been adding as little water as possible to the paste and even using a hand-mixer/blender to finish the dissolving of the paste in the warm water, I then add Goats milk powder to further thicken it with honey powder sometimes. It stays emulsified and is really thick like body wash.
I have heard good things about Guar Gum if you don't mind clowding which if yout adding milk powder or want a body wash, then it does no matter. I am going to try it next time.
The above thread about Gum Arabic is interesting and I will give it ago as well as cause it seems to leave the soap a bit moe clearer then the Guar Gum.
This has been just my experiences and others may have had completely different ones, experiment to find your favourite way. I personally don't see what all the hype is about having clear soap.
I forgot to mention that I do not like to use Borax, it makes gel real nice and easy with soft oils, not so good with hard oils like CO. But I find it dries the hell out of my skin, I also read some studies and research that indicate it can contribute to male infertility and such, I mean there is all kinds of debate around Borax, but the way I look at things, "where there is smoke, there is fire". I have used it though and probably will find a use for it again in the future.