I'm looking to make an outdoor sign to mark our property. I'm thinking of hanging a 48Lx36Hx2T slab of wood from a post and beam frame. I am trying to think of where I can affordably get a slab of wood to use for the sign. Any suggestions?

I have thought about laminating a bunch of 2x4s or 2x6s, but concerned that once I cut them square they'll bend all out of shape and it won't work. Plus I need to figure out an outdoor glue that will withstand the elements.

Looking for any other suggestions!