Slow cooker sweet and smoky beef

beef chuck roast

medium onion, peeled, cut in half, and sliced into thin half-moons

can frozen unsweetened apple juice concentrate, defrosted

dried thyme leaf, or 1 tsp fresh thyme leaves

honey

large chipotle pepper in adobo, chopped, plus 1 Tbsp adobo sauce

Kosher salt

Fresh black pepper

cornstarch or arrowroot