Step 4: Finishing up (that was fast, right?)
2. Cut two pieces of yarn. Thread would work to if you wanted it to be less noticeable but it isn't as strong.
3. Use those two pieces of yarn (or thread, whatever floats your boat) to tie knots on the overlapping area.
4. Trim the knots.
5. Pull those knots toward the edges (the double knots you made earlier).