Prepare your vegetables: Finely slice them in 2-3 mm (0.1 inch) thick circles and arrange them in any order you like. I put a slice of eggplant, then zucchini, tomato, onion, bell pepper. Fill your form tightly with overlapping vegetables, arrange them in circles or rows, depending on the shape of your form. I used 13 x 9 inch pan (33 x 22 cm). Make a try-out to estimate if it’s enough slices. If not, slice more. It’s hard to predict how many vegetables you need, as it depends on their size and on the size of your dish. If the difference between the sizes of your slices is too big (normally, the eggplant has the biggest diameter), you can cut rounds out of the large slices. Cut a section off the bell pepper rings to make them smaller and hide the cut-out pieces on the bottom. After you are done determining the amount of veggies needed for your ratatouille, empty the dish.