1 stake in the center, rear of the tarp.
1 stake holding your hiking staff guy line.
1 stake at each front corner.
The tension on the lower triangular sections will hold them down pretty well. You can fold the corners under you as a partial ground cloth, too. Note that you can also do away with the front stake holding the hiking staff, since the angle lets the front corner stakes hold it up. But, it is not good in any wind.