In high school 20+ years ago I used to collect 2 liter bottles from family and friends. Paint the bottles black with 1 white strip. We were really cheap but my friends and I would use cheap 25 lb fishing line and anything from rocks, sections of bricks I collected working for a brick layer, and what ever metal scrap as weights. You will be suprised how many bottles you can collect in one week. I believe my junior year we had about 150 of these bottles that we hunted over on one marked blind spot we had on the lake systems where I grew-up. We left them out all season and I am sure alot of other people hunted this spot because by end of season when we picked them-up and tore down the blind there were 100s of shells people left in the blind from wiggling their way down through the oak tree branches and other debris we had piled on the blind. To get them to stay on their sides we would use elmers glue with a long piece of tube to squirt on the inside of the bottle from where the radius of the neck stops to the bottom of the bottle and then fill with a couple tablespoons of sand to shake into the glue. Let dry in the sun and then paint. Some of us would make 30 or 40 a summer and just repaint the same bottles every year.
My grandfather used two coffee cans he soldered together with an eyebolt bolted into the bottom of one can. Painted black with a white stripe. During the offseason he used the cans as jugs for catfish. I hunted several times with him growing-up over 50 of those he used and in the spring would float the Ohio for catfish with the same cans.
On Reelfoot Lake in Tennessee some of the handed down family blinds on the lake have gas tanks, foam and in fact you name it painted black to make massive spreads with the actually decoys in the holes where they want the birds to land.
The cheap decoys will get the birds attention and easily put them into shooting range. It is an unorthodox technique but it does work. People will look at your funny but you will have birds in the boat with little expense.
More traditional concepts in making your own would be to look into Y-Boards, sleds, or even sillohuettes with wide bottoms you can make from wood which will last much longer when shot...Of course wood and cork carved decoys is the sure thing!!!!
Regards,
Kristan