A while back, I got tired of having to keep my tent buttoned up at 17th C reenactments, because of my modern plastic cooler. I also got tired of schlepping a blanket around to cover it. I'd seen several members of Duke Sir Timothy of Arindale's household using period chests with coolers in 'em, so decided to try my hand. This is my version, you can vary it to suit yourself. I also used pine boards, modern nails, and modern fittings for economy and convenience. If you want to go with hardwood, and period nails / fittings, this is also good.

NOTE ON MEASUREMENTS: A board sold as a 1" x 12" isn't. It's actually a 3/4" thick x 11" wide board. Likewise, a supposed 1" x 10" is actually 3/4 x 9-1/4. This affects measurements.

MATERIALS:

1x12 board, 6ft 1 Front / back / lid
Cut into 3, 2ft pieces. Mark your 1x12 in thirds, and cut to the OUTside of the lines. The two short pieces are your front and back, and your lid winds up about 1/8" longer due to saw cuts. (fig 1).

1x10 board, 8ft 1
Cut into:

Do NOT measure and cut the bottom (nominal 1x10, 22-1/2") until after the legs and sides are together, then cut it for a snug fit. The same goes for the interior partition, nominal 1x10 by 10-1/4". Measure and cut the partition AFTER the bottom's in.

(fittings usually come with their own screws)

Linseed oil, paint, stain, or other finish

TOOLS:

Bits slightly smaller than your nails & screws
Tape measure
Combination or framing square
Hammer
Paint Brush
Serrated Knife
A Workmate or similar bench with vise / clamp capability is useful.

PROCEDURE:

1. Cut your front, back, and lid, as well as your two 18" legs. (fig. 1)
2. On the front and back, drill holes for nails as shown in fig. 2. Draw lines 3/8" in from the edge on the ends and bottoms. Space the nails to suit yourself, I used 3" gaps.
3. Set the legs up on edge, and holding one leg flush with the end of the front, drill the top nail hole into the leg. Lightly tack that, then drill the bottom hole. Pop the boards apart, apply a layer of glue to the leg, and nail the top and bottom. Drill and nail the two middle holes, nailing each as you drill. Repeat for the other leg. (fig. 3.)
4. Now, repeat the preceding step with the back.
5. Measure and cut the bottom for a snug fit, without being so tight the legs pop out. Fit it in place, and drill the outer nail holes in the bottom rows, front and back. Remove the bottom, put glue around the edges. Re-fit, and nail front and back. Drill and nail the remaining holes (fig 4.)
6. Measure and cut the center partition board, making sure it's even with the top of the chest (fig 5.)
7. Take a break from woodworking, and pop the carrying handle and lid latches off the cooler. Done gently, this should leave the plastic grommets in the sides without tearing the foam. Put the cooler into the chest, and line up the partition so the cooler's snug, side-to-side (fig 6).
8. Mark the partition location, and pull the cooler. Glue the partition in, and add nails up near the top in front and back, and a couple through the bottom.
9. Attach the hinges and hasp to the lid, following the instructions therewith, then attach the lid.
10. Likewise the handles, putting them up fairly close to the top.
11. Using the serrated knife, cut the flange off, all the way around the styrofoam lid of the cooler (fig 7). Lightly insert the lid into the top of the cooler. Coat the top of the lid with carpenters' glue, then firmly close the wooden lid down over the styrofoam. Let dry overnight, to fix the styrofoam lid to the wooden one.
12. Voila, it's about done. Paint, oil, or finish to your taste.