The cockpit coaming is applied in three steps; glue in the coaming spacer, glue in the coaming, then fiberglass. The coaming spacer comes in two halves that fit together with a small puzzle joint at the front and rear of the cockpit. It is glued down with epoxy thickened with cell-o-fill, using as many clamps as one can fit around the perimeter. I took care to clean as much of the squeeze out to minimize scraping and sanding once the epoxy sets. Note the plastic inside the boat to protect the hull and foot braces already installed.
Next the coaming in glued using basically the same approach.
Before fiberglassing the coaming it needs to be rounded over on the top where the paddler will enter, sit and exit. Also all of the squeeze out sanded off and everything smoothed. Then a large piece of fiberglass cloth is laid over the cockpit and held in place with a few pushpins. The deck is masked to keep it free from drips. The cloth is epoxied in place, and cut out when the epoxy has hardened sufficiently.
Here the kayak is fully glassed and coaming applied, next comes sanding and lots of it.
Building and Restoring Small Boats 