Roughly chop 1 yellow squash and 1 zucchini.
In a sauce pot sauté the chopped squash, garlic, and onion in 1 tablespoon of olive oil.
Add sauce to the pan and bring to a boil.
Reduce heat to low and simmer 30-45 minutes.
Thinly slice the remaining squash using a mandolin.
In a bowl beat the egg and add the ricotta cheese, salt, pepper and parsley. Mix well and refrigerate until ready to use.
Assemble the vegetable lasagna in the bottom of your crock pot using the following steps.
Spread a scant ¼ cup of the sauce over the bottom of the crock pot.
In a single layer cover the sauce with a layer of yellow squash slices.
Spread about 3 tablespoons of sauce over the squash.
Spread about ¼ cup of the ricotta cheese mixture.
Top with a layer of cheese.
Repeat 3 more times, ending with a layer of mozzarella cheese.
Cook on high for one hour. Reduce heat to low and cook an additional 3 hours or until the center is cooked through and the squash is tender.