You might see here in these clamping shots that I have modified the left over foam as jigs.

The cores come cut with the waste foam in place and if you trim down an inch at the join lines these make excellent jigs to help hold things while gluing together the main pieces. This is easiest to see in Pic 2.

The trimmed area allows you to ensure the join is acurate and to wipe away some of the excess glue while it cures.

FC3 clamping

Fc3 clamping setup

FC3 cores ready