Prep the aromatics: Zest one lemon, then squeeze both lemons for juice. Mince the garlic and slice the onion.
Season the chicken: Pat the chicken dry.
Sprinkle generously with salt, black pepper, and half the oregano and thyme.
Optional quick sear: For deeper flavor, heat 1 tablespoon olive oil in a skillet. Sear chicken 2–3 minutes per side until lightly golden. This step is optional, but it adds nice color.
Layer the crockpot: Add onions to the bottom of the slow cooker.
Place chicken on top. Scatter garlic, lemon zest, remaining oregano and thyme, and bay leaf over the chicken.
Add liquids: Stir lemon juice with chicken broth and olive oil. Pour the mixture evenly over the chicken.
Add a pinch of red pepper flakes if you like a little heat.
Cook low and slow: Cover and cook on Low for 4–6 hours, or on High for 2.5–3.5 hours, until the chicken is tender and reaches 165°F internally.
Finish with brightness: Taste the cooking liquid. Add a bit more lemon juice or salt if needed. Stir in olives at the end if using.
Serve: Spoon the lemony broth over the chicken.
Top with chopped parsley or dill. Add crumbled feta if you like. Serve with rice, orzo, roasted potatoes, or a Greek salad.
Optional sauce thickener: For a silkier sauce, whisk 1 teaspoon cornstarch with 1 tablespoon water.
Stir into the hot cooking liquid and simmer uncovered in the slow cooker for 10–15 minutes, or bubble on the stovetop until slightly thickened.