Mix the masa and water together into a smooth consistency for about 3 to 5 minutes. If working in large amounts cover bowl with a damp towel to keep from drying out.
Take a piece of the dough about the side of a cue ball, and roll into a firm ball. In a tortilla press or with a hard flat book or cutting board, line with 2 pieces of plastic. Place masa ball in the middle and apply pressure until ball pushes out to 4 to 5-inch diameter. (if edges of patty are cracked deeply the dough maybe too dry or if the patty does not remove from the plastic easily the dough maybe too moist.)
Heat a cast iron pan to very hot. Place masa patty on pan without any oil, brown on both sides, approximately 1 minute on each side. Remove and let cool.
While still warm, remove the center of the dough, and form the edges up, making a hollow tart like shell.
Heat 1-inch of canola oil to 350 degrees F. Add sope shells to oil and cook on both sides until crispy and golden brown. Hold warm for service.