Which epoxy should I use for a thick charcuterie or serving board?

It depends on the thickness of the pour, and it usually takes two products.

For any pour 1/4" or thicker, whether a board that is 1/2", 1" or 2" of solid epoxy or a river-style board with a wide channel, use UltraClear Deep Pour Epoxy. It's a slower-curing 2:1 resin made for clear casting at depth. A 1" layer can be poured in one go, and thicker boards are built up in additional layers 12 to 24 hours apart.

If wood is part of the board, seal it first with UltraClear Bar & Table Top Epoxy or UltraClear Art & Craft Epoxy before the Deep Pour goes in. Art & Craft Epoxy pours in 1/8" or 1/4" layers with a 30 to 40 minute working time; it's made for artwork and crafts, not deep pours.

Deep Pour Epoxy isn't rated for hardness. It cures very hard to the touch, but it's softer than Bar & Table Top Epoxy, which cures to a Shore D hardness of 98 and is our most scratch-resistant finish. So once the Deep Pour has fully cured, top coat the board with a flood coat of Bar & Table Top Epoxy. Art & Craft Epoxy also works as a final layer, but Bar & Table Top is the more durable choice for anything that sees daily use. The process is the same as a river table: https://ultraclear.helpscoutdocs.com/article/859-table-top-epoxy-deep-pour-epoxy-river-table

Whatever you build, it's a serving board, not a cutting board. Don't cut on any epoxy surface.