Here is a picture of the table I made for Thanksgiving. My DW needed to seat 16, and we wanted to do it all at one table, which is set up in our living room.
The table is 12 feet long by 4 feet wide. It's made of 2 sheets of OSB (each cut to 5 feet) with furring strips screwed around the underside of the edge to stiffen it. This is sitting on top of 3 small plastic tables.