Some DIY cat hammock projects re-purpose existing items to function as stands or simply attach the hammock to an existing structure. The item may be used as is or modified as part of the project.
A wood stand for a cat hammock can be built from wooden dowels, boards cut to length, or a sheet of plywood or some other material cut to the right shape.
Although you could set up a full-size human hammock for your cat to use, you may want to buy or make a hammock specifically for your cat (it's cheaper and takes up a lot less space). A cat hammock may or may not actually resemble a hammock as humans have come to know them.