Yes, UNDERLAID is a Scrabble word!

Letter values in Scrabble US: U 1, N 1, D 2, E 1, R 1, L 1, A 1, I 1, D 2.

Is it a valid word?

UNDERLAID is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

raise or support (the level of printing) by inserting a piece of paper or cardboard under the type
put (something) under or beneath
provide with a base, support, lining, or backing