to make a four foot square solar dehydrator, you will need:
half sheet plywood (4' x 4')
16' 2 x 4
4' x4' sheet of plexiglass or similar clear plastic
4' x 4' hardware cloth
assorted nails or screws
small can of flat black non - toxic paint
common carpentry tools
cut the 2x4 into two pieces 4' and two pieces 3' 9" and nail to the plywood forming a shallow box with the plywood as the floor and the 2x4's as the sides.
drill three or four one inch holes in each of two opposite sides.
cut the hardware cloth to fit inside the box.
paint the inside of the box black, and allow to dry.
drive four small finish nails on the top edge of the 2x4's - one at each corner, leaving a half inch sticking up.
position the plexiglass over the box and mark the positions of the nails on the plastic with a magic marker. drill a hole at each mark. large enough for the nail with a generous margin.
lay material to be dried one layer thick in the box, cover with the plexiglass and put it in the sun. prop it up about 30 degrees to face the sun. the sides with the holes go at the top and bottom.
the sun's rays will warm the box and the air in it. the warm air will dry out the material you are dehydrating. warm air rises. this is what the holes are for. the warm moist air leaves through the holes at the top , drawing fresh air in the bottom to be warmed up and to take up more moisture. the hardware cloth is to keep the material off the bottom of the box so air can circulate, at least a little, on both sides.
simple, easy, cheap. no?
the dryer can be any size you want, but 4' x 4' is easy to handle.