All you need to make this tent is: one cardboard box, piece of old net curtain (or something similar) and some sticky tape.
Let your cat know where the food is by keeping the flap half open. Once your cat is going in and out of the food tent quite happily, you can then keep the flap down. I have found that this has kept the flies out of my cat's food this summer.
Food tent half open Food tent in action!