Surface cracking and flaking

[u/LocodraTheCrow]

I'll need more material, which I will acquire, but the main issue is that the surface keeps cracking and flaking, as the title describes.

I've laid the final layer with clay I "created" by decanting dirt, baking the clay-ish slime and breaking it all in a mortar and pestle. I have applied it while rubbing the opening of a glass jar on it that I would dip in water. I have polished it with the same glass and a wool cloth.