Step 2: Gluing to the base
Cut the base to the right size, leaving a little room all around to ensure a solid connection. In this example I used mat board for the base, though ordinary corrugated cardboard works equally well.
Put a few drops of glue on the bottom of the rolls and use these to mark the "footprint" of the rolls on the base.
Now trace the footprint with lots of glue and put the rolls on.
Put something heavy on top of the rolls while this dries to keep the base from bowing or wrinkling.