years ago I made my own incubator . It had 3 trays and took about 200 or so pheasant eggs per tray . The heat was supplied by a row of light bulbs fixed on a board with the light part placed in holes ,cut in the side of a pipe made out of empty tin cans . Above this I made a tray to take a small amount of water ( like the old paraffin greenhouse heaters) , I used a thin layer of sponge to help prevent water getting tipped everywhere.
The heat was controlled by adding or subtracting light bulbs from the rack , till I found out the number needed in watts .
The water, I just kept it moist but not wet . In this incy I hatched hundreds and hundreds of chicken , guinea fowl , quail , ducks , geese, peacocks and thousands of pheasants . It cost me about £5 to make ....( it was 30 odd years ago ) out of a couple of sheets of ply and some 2"x 1" , a few light bulb holders , and a few other bits and bobs I had laying around .
It worked perfectly , apart from I had to turn the eggs by hand . The thermometer was an old fish tank one and I never had anything to test the humidity.
A tray of some kind with a bit of sponge/old towel, would provide enough moisture .
hope that sort of helps ....?
cheers
Russ