Toyota Prius Sub Enclosure - How-To Built-To-Fit Enclosure

With a piece of chipboard from the inside, I covered a cutout in the plastic tray before applying the tape.

I covered the entire inside and outer lip of the plastic storage compartment with blue masking tape, along with the cubbyhole above.

Since the enclosure will be made in two pieces, I taped them up separately.

Then, I masked and covered the entire area around the panel where I'll be laying fiberglass.

Next, I used spray adhesive to separately cover both the plastic tray and the panel with foil. Foil not only helps protect the car, it also makes for an easier mold release.

Fiberglass pieces were cut to fit in the plastic tray and fold over the lip. I cut enough pieces for two layers of 3-ounce mat. Then, I applied sanding resin with some Cabosil mixed in. The Cabosil will thicken the resin and help keep the fiberglass from falling off of vertical and inverted surfaces. It also helps the resin act as gap filler, without even changing the properties of the resin.

After the fiberglass cured, the edges were trimmed and the top lip was smoothed out a bit.

I placed it back in the car for the next step.

Two 3-ounce layers of fiberglass mat were cut to fit and applied to the panel with a resin and Cabosil mix. The Cabosil especially helped in this inverted situation.