You may have some luck with stabilizing it as though it was a slab. Using an epoxy in acetone method:
- Dissolve epoxy in acetone
- Submerge rough stone in the epoxy acetone mixture
- Seal up container so acetone does not evaporate
- Leave in mixture for at least a week
- Remove from acetone and let dry for at least another week
The important detail is this method relies on diffusion. When you have a slab your path length is relatively short, so the epoxy can diffuse in fairly quickly (days). As you make the material thicker the time increases. If you have a piece of rough that is fairly narrow in one dimension, you're in luck, treat it as a slab, diffusion won't be slowed down by rough edges, indeed it will be slightly faster. Where you're going to run into problems is with a thick piece of rough material that resembles a sphere. In this situation you may want to go at it in multiple passes as follows:
Let's say that your rough material is sphere with a diameter of six inches. Additionally you've determined that you can "completely" stabilize a slab that is one inch thick.
If you follow the same procedure with the rough material, you can "completely" stabilize the outer 1/2 inch of it. At which point you could cut off slabs as circles of a sphere:
of 1/2 inch thickness.
The process could be repeated to allow for a second, larger, slab to be produced.
I would probably sacrifice the first layer, as it is typically irregular to begin with, making a poor slab. Or, because I am impatient, I would slab the rough and accept what breaks as broken and stabilize the usable parts as slabs.
Note: It has been years since I've made a cab and my knowledge of stabilization techniques is from research only, I have not tried these techniques myself.