My Uncle taught me to make nets when I was a boy. It isn't difficult and the tools are easy to make. I would recommend finding a commercial fisherman and asking him to let you help mend his nets.
Depends on how far you want to take it. The simple anwser would be to buy netting, cut it to size then attach the boarder lines, floats and weights. Now if you want to go all the way down then it still isnt all that hard but becomes rather time consumeing. First is to get or make a LOT of cordage. Now while it may not be the best way, the simplest way I know of is to run a top line and tie it off at both ends. Now say you want 2" mesh, tie a line to it every 2" and cut it about double the length you want for the height of the net. For explaination count them off 1-2-1-2... Now go across and take each '2' and tie it and the '1' to its right together with an overhand knot 2" from the top. Next you take each '2' and the '1' to its left and tie them together in an overhand knot 1" below the other knot. Keep alternating like that and tieing each knot 1" below the other untill you get to the bottom all the way across. Like I say, Im sure there are other ways (probably easier and or better) to do it but I had the same question and anwsered it with a spool of line and an afternoon at the clothes line and this meathod WILL get you a functional net and like I say is simple to do, just time consumeing and I would HATE to have to be MAKEING the cordage to make a net.....it takes more line than you probably think. Say 5'x5'x2" mesh, I would estimate at LEAST 300' of line and that would be concervative and hopeful to get the full 5'x5'. Thats also something like 1800-2000 knots to tie...and I may be shorting the numbers..... After the experiment I bought a net to be sure I had it on hand.
