Toss sweet potato slices in a large bowl with oil, 1 t. sea salt, and ¼ t. freshly ground black pepper until potatoes are coated in oil and spices.
Line a rimmed baking sheet with foil, and spray with PAM Cooking Spray.
Arrange potatoes in a single layer on the baking sheet (I put the largest, fattest slices on the corners and along the edges, since that is where the heat concentrates.)
Cover tightly with foil.
Place on middle rack of a cold oven.
Turn oven to 425°, and roast for 30 minutes.
Whisk maple syrup, melted butter and thyme together.
Remove baking sheet from oven, and CAREFULLY remove top piece of foil. (The steam will come rolling out, so be CAREFUL!) Return pan to oven, and roast potatoes, uncovered, until bottom edges of potatoes are golden brown. This took me only 15 minutes, but your oven may vary.
Using a pastry brush, brush the potato slices with the glaze.
Now carefully turn the potato slices over using a thin bladed spatula, and baste the other side as well.
Return potatoes to the oven and continue to roast an additional 15 minutes or so (your oven may take longer) until bottom edges of potatoes are golden brown. Let cool for 10 minutes, and serve.
