We have clay in our yard. I have spent a good two hours digging out the square space under our slide area of our swing set. I dug deep enough to have deep enough sand for the kids. However, due to the clay bottom I'm concerned in getting standing water inside after rain or when using the hose. What can I do to ensure drainage? Any suggestions? I'm ready to put weed fabric down then sand. Our swing sets sits on a bank so there is a slope behind the set itself.