Do I need to seal concrete before pouring epoxy, and how do I prep it?

Yes. Seal coat the concrete with UltraClear Bar & Table Top Epoxy first, then pour the flood coat over it. The epoxy bonds well to raw concrete, but the surface has to be clean: wipe it down thoroughly with denatured alcohol or acetone to remove dust and residue. Stick to those two cleaners, since they evaporate without leaving anything behind. If the counter is old, pitted or worn, clean it, repair the damage and sand it before you start.

The seal coat and the flood coat are the same product applied differently. The seal coat is brushed on thin. The flood coat is poured on and left alone to self-level to about 1/8" thick; don't brush or spread it.

1. Brush on the seal coat. 2. Wait 4 to 6 hours. The seal coat will still be tacky, and that's what you want; pour directly over it. 3. Pour the flood coat and let it self-level. If more than 10 hours pass before you pour, lightly scuff the seal coat with 220 to 320 grit sandpaper and wipe it with denatured alcohol or acetone first.

The same process works on brick counters. If the top has a wood border, seal coat the wood as well, and seal every seam in the border with latex acrylic caulk before pouring so the flood coat can't leak out; losing epoxy through a leak can cause curing problems. Use silicone caulk only on temporary dams, since epoxy won't stick to it.

Full instructions: https://cdn.shopify.com/s/files/1/0320/7168/0140/files/Epoxy-Instructions.pdf?v=1616443869