The short answer is: don't.
We had this train table that the kids don't use anymore, and I thought I'd be clever and repurpose it. Looked on Amazon - lego base plates cost HOW MUCH? But I need 15 of them! So ordered some non-LEGO ones. They still cost $80. Then I went to Lowes, got them to cut down a piece of wood ($20 - I had to pay for the whole sheet of plywood even though I only wanted 1/3 of it) and bought spray adhesive ($20), as per the instructions I found on google. Got home, sprayed the wood, let it lay on the lawn while I frantically tried to piece together all those base plates only to have them fall apart on me when I lifted it up, so I'm piecing them together in the sun, trying to do it before the adhesive dried while keeping bits of grass out of it. Put a piece of plywood on it to stick it down and left it for a while. Then I carried the thing down to the basement - LEGO baseplates falling off it like leaves. Apparently spray adhesive is not going to work. Back to Lowes, asked for advice, they suggested epoxy, bought two tubes of that ($30). Spent another half hour mixing it and scraping it onto the base plates, having to make every drop count to get through it all without having to go back for a third tube. Finally get the thing together - it looks fine. Show it off to the kids. They are underwhelmed. Google LEGO tables, find a Kidcraft one on Amazon for $89. I spent $150 and hours of work. Today my thumb is all red and sore from pressing blocks down to try to space the base plates evenly.