Easy Heart-Healthy Scalloped Potatoes (No Cream)

Ingredients

• Non-stick cooking spray
• 6 medium potatoes, peeled and cut into 1/8-inch thick rounds
• 2 Tbsp olive oil
• 2 Tbsp unsalted butter
• 1 1/2 Tbsp fresh thyme, divided
• 1/4 tsp Kosher salt, divided
• 2 large yellow onions, peeled and thinly sliced
• 2 large garlic cloves, finely minced
• 2 tsp dried sage
• 1 tsp freshly ground black pepper
• 1 2/3 cups unsalted vegetable stock