I still think that necromancers or zombie uprisings should make cremations a more readily used form of burial.
...or maybe "Perhaps let's
not bury Uncle Urist McDigger with his favourite pick... And can we possible put some more soundproofing around Aunty Urist's tomb?"
Traditional Earth traditions[1] aimed towards the prevention of Undead issues generally rely upon additional measures such as head-severing, heart-staking, a general (yet reverent) dismembering and separation process, as well as some less severe-looking measures (of the kind that don't
also guarantee that the assumed-deceased might not wake up from a more mundane undiagonosed deep slumber) such as burial at a crossroads, or with a range of culinary additives (from garlic to lemons...) being laid upon their person or within their mouth...
Given the "if it can grasp, it can rise" nature of the Dwarfworld dead, then dismemberment is probably not the answer, but "having
really heavy rocks placed on top of the sarcophagus" sounds like a good tradition to me. If it
must involve heat, then filling the room with magma sounds good, and matches (especially for some people) the general consensus about dwarven psychology.
But, how about more work for the engravers... Obviously slabs are there for the unburyable dead, but if there is knowledge to be gained in order to
become a necromancer, then there might be a civil-knowledge of a sigil (pick any two or three symbols from the currently available pantheon and create "a circle combined with a square, overlaid with the wavey pattern of water", or "a symbol representing lust, within a triangle") that must be engraved upon a sarcophagus (any that has not already been isolated, so that it doesn't matter) to prevent the occupant from taking up a newly reanimated disposition... And given we now have books, parchment/vellum/whatever's-appropriate scraps with the given symbol drawn upon could be a stop-gap measure for as-yet-unburied corpses (or those of enemies, yet to be more permanently disposed of), placed upon each body[-part] at risk... With these items becoming more and more x<Worn>x as and when the local influence of a necromancer is actively felt, and the protection starts to do its job in deflecting the revivification effects.
Maybe this also makes work for the embroiderers of clothes, with an explicit job for the creation clothing bearing this symbol ending up with attire that gives a similarly temporary respite from 'conversion', post-mortem. And/or useful for the living, insofar as an anti-vampiric deterrent (although not a perfect and permanent one, or certain symbols being specific to certain vampires, culture-wise). But I fear that in my flight of fancy I've drifted
far from the original subject of this thread, drifting well off into other practices and applications.
[1] Whoops, tautology there...