The OP specifies “skull” meaning, I presume, the bones and teeth. Just putting the decapitated head on an ant pile (or in a box of museum beetles) will not usually result in a skeletonized mount. The skin is quite tough; if it dessicates before the bugs remove all of it (and that is the common experience) then the result will not be a cleaned skull. Some preparatory work is required.
The head should be skinned and as much tissue as possible removed. Then consign it to your favorite or most available hungry bugs.
CAREFUL!!! (sorry, caps seem required)
Reflexive biting isn’t the only danger. You will also be removing two quite large venom sacs, these being in the big bulges on each side of the head. The venom remains active. It will cause you serious distress, potentially even cause your death, if any of it gets into a break in your skin or into your eyes. (You could though drink it-- unless you have open sores in your mouth. It is highly modified saliva, after all. But this is NOT RECOMMENDED!!) Gloves and extreme caution are required.
Boiling the head is useful. It will help to break down the skin and other tissue, facilitating removal. And it may also denature (inactivate) some of the lethal proteins in the venom. Do NOT though assume total safety even with a boiled head. Great care is still required. But this will result in a much better presentation mount.
I do NOT recommend that an amateur or a clumsy individual attempt this. Cleaning venomous snake heads is best left to professionals or people with a death wish. But if you want a quality mount, this is the technique.
If you try it, and you notice any unusual physical symptoms in yourself, seek immediate treatment for envenomation, exactly the same as if you were bitten.
Point of information: I have been handling venomous snakes (meaning live ones) for more than 40 years, without being bitten. I did though once manage to envenomate myself with a dead snake. Take it for what it’s worth…