Cheryl, a 9" x 13" top crust is about the same size as the 12" round you'd use as a top crust for a 9" pie. Not sure if your slab pie includes a bottom crust? But if so, you'd need about 2 crusts' worth for the bottom. So three single crusts total should do it without a problem. PJH
November 16, 2016 at 2:30pm
In reply to I would like to know approximately how much crust I would need … by Cheryl (not verified)