I've listed 25 different tarp shelter designs to help you get started. Each configuration has its pros and cons and there isn't really a perfect design for all occasions. You'll have to chose the right one depending on your situation or you could just try
I saw this done at a festival in Scotland. The cordage did not sting. Find out how to make string from stinging nettles without getting stung! Nettle cordage can be used for lots of things, such as fishing line and shelter building.