Throughout cooking this recipe, if the pan is drying out before your vegetables are cooking, put the lid on (not tightly), to keep some of the moisture from evaporating.
Add the red pepper, zucchini, and yellow squash, moving the vegetables to the side to add more oil to the bottom of the pan (so it can heat and not just soak into the vegetables) if needed.
Cook until the vegetables soften, about 5-7 minutes.
Add the garlic, and cook until fragrant, or until it seems incorporated.
Add the tomatoes and lower the heat, stirring occasionally, for 5-7 minutes, or until all vegetables are tender and incorporated. The tomatoes should add a little liquid to the mix.
Stir in the oregano, thyme, fennel seeds, and coriander, and cook the mixture, stirring, for 1 minute. Add salt to your taste.
If you are using basil, stir in sliced ribbons after you have removed the ratatouille from heat.
Notes
Leave the skin on all of the vegetables for color and nutrition, unless they look waxy and tough to you. Chopping shapes are just suggestions; as long as everything is relatively small and approximately the same size, you should be all set.
Recipe by My Utensil Crock at http://www.myutensilcrock.com/2018/08/28/ratatouille/