Many years ago I built one from the plans posted by Deb.Worked well but I recently built a new one that is more efficient.
A few tips.
Make your pan and wire basket wide enough to accept a deep box.The depth of the pan only needs to be 5-6ins but the interior of the melter should be deep enough to hold the box.For shallower boxes you can place pan on a few bricks to keep it close to the glass
It is much easier to melt frames a box at a time.If you use grooved BB,melt frames upside down to keep wax out of groove.
Make your basket out of 1/2 hardware cloth and always line with paper towels to collect slumgum.This makes it easier to clean and gives pretty clean wax.Set basket on wood strips to keep off the bottom of pan.Spray paint pan black.
I use a silicone baking pan to collect wax and honey.(3×6×8?? but bigger is better) The flexibility helps to get the block out.This sits in a larger pan I folded out of flashing to collect spills.
Don't bother with a front door.Too complicated.Design with room to tilt your collection pan sideways to remove it.
This may be obvious but....Remove collection pan in the morning when cold and clean off paper towels and basket in the evening while still hot.
My double glazing came from an old metal exterior door.Worked great.If you try to make your own from 2 pieces of glass you can get leaks and water between the panes will fog and condense.An alternative would be to find a double glazed window and design around that.
Make your lid slightly larger than the wooden box and seal with weatherstripping.I use a strip of drip edge on the top edge of the lid to keep out water.Again,water will fog your glass if it gets inside.
For insulation I used the foil faced foam and the foil reflects on to the pan.Pink or blue foam sheets can melt or distort.
Design with wheels on the back and a sturdy handle on the front.You won't regret it.I used 1/2 CDX for sides and bottom with 3/4 pine for lid,legs, top edge and corners and I bet it weighs 75 lbs or better(glass is heavy)
Use pressure treated for anything in contact with the ground.
This is important.Design with sun angle in mind. You want the sun to hit your glass and your pan as close to 90° as you can get. Check a solar panel web site to find the optimal angle for your lattitude.My first design was too flat and did not work well inAug and Sept.
Good luck