The bed is a rather simple affair as there are only very few options to build it:
Phenolic resin bound sheet at 1mm, common product names are: Pertinax, Hartpapier etc.
As we are printing on the phenolic resin surface the exact type of fibre bound within doesnt really matter.
Its compatible with pretty much any material extrudable, Dry sand the surface with 400grid, attach it to the aluminium bed with 3M 468MP.
Again there are no other options than exhaust insulation, comes in slightly under a mm, one side aluminium foil, sandwiched glassfibre in the middle, self adhesive high temp resisting sheet on the other.
Dont use aluminium ones, way to heavy, printed holder are perfectly fine here.