An easy one to build is to use a broken recurve bow as the lancher. You cut the broken part of the bow off at the fadeout, then mount it to a piece of plywood of about 3'x 3'. This is done with two screws through the riser and plywood. Spacers should be used to keep the bow limb clear of the plywood when in use. Tie a loop on the bowtip that will allow you to use it with a release. Then mount a mechanical release on the plywood far enough from the limb tip to permit some adjustment. This will allow a quail or pheasant shot of 30-45 degrees.
The same set up will work for discs, but would require using two pieces of plywood bolted together with the right distance for the disc being used. Then it could be used for 90 degree lanches.
I built one of these once but we never had the right area to use it.