How to make a winter hammock.

[Girotogo]

I will be using some 30D waterproof material to make a winter tarp. Should I use pins and then sew? Do I need to seal it later? I've read that the material is light and thin and slippery. Any special tips on sewing this material. I was thinking to use velcro to close the doors..is this overkill? Is it hard to do? Thanks in advance for your wisdom.