Slow Cooker Sausage and Vegetable Ratatouille

uncooked, crumbled spicy Italian sausage (not in casings) (see NOTES)

large red bell pepper, ribs removed and cut into 1" squares

large eggplant, cut into 1" cubes

zucchini, trimmed and cut into 1/4" half moons

large yellow onion, quartered and thinly sliced

to 4 medium cloves garlic, crushed or finely chopped

jar pasta sauce (see NOTES)

kosher salt

fresh basil (or parsley) for serving