Do I need to seal coat the wood before filling cracks with Deep Pour Epoxy?

Yes. Brush a seal coat of UltraClear Bar & Table Top Epoxy over the bare wood, including inside the cracks and voids, before you pour UltraClear Deep Pour Epoxy. Deep Pour can't do this step itself: it is only for pours 1/4" thick or more, so it can't be used as a seal coat or as the final top coat over the surface and sides.

One exception: if you're tinting the Deep Pour to a fully opaque, solid color, some users skip the seal coat because bubbles won't show in the colored fill. We still recommend sealing first, with or without pigment.

The full sequence for a table, bar or countertop: 1. Seal coat the wood with Bar & Table Top Epoxy. 2. Fill the voids with Deep Pour until they are level with the surrounding surface. Pouring it in 1/4" layers lets the air bubbles pop before you keep filling. Voids deeper than 1" are poured in 1" layers every 12–24 hours. 3. Let the Deep Pour cure for 3 days. 4. Lightly scuff-sand the cured fill with 220–320 grit and wipe off the dust with a clean, lint-free rag and denatured alcohol or acetone. 5. Seal coat and flood coat the whole surface with Bar & Table Top Epoxy. Old barn wood usually needs 2–3 seal coats before the flood coat.

Guide: https://ultraclear.helpscoutdocs.com/article/859-table-top-epoxy-deep-pour-epoxy-river-table