All Natural Soap can seem to give you trouble but really its simple. All you need to not have a mushy bar of soap that doesn’t last is a soap dish. But not any soap dish will work. You need to have a draining soap dish so that your soap can dry in between uses.
Soap gets mushy when it doesn’t dry and is left on a flat wet surface or a soap dish that has water in it.
Here are some photos and links for good soap dishes. You can also type in the name of the soap dish in google and find the price range that fits you.
I use a metal rack that hangs from my shower and I put my shampoo and my bar of soap on that.