In a large bowl, gently combine turkey, panko, half the garlic powder, half the thyme, half the stock concentrates, 1 TBSP water, 3⁄4 tsp salt, and pepper (use all the garlic powder, all the thyme, 2 TBSP water, and 11⁄2 tsp salt for 4 servings). Form into two 1-inch-tall loaves (four loaves for 4).
Place meatloaves on opposite side of baking sheet from carrots; roast on top rack until meatloaves are cooked through and carrots are browned and tender, 20-25 minutes. TIP: If carrots are done first, remove from sheet and continue roasting meatloaves. (For 4, use two baking sheets; roast on top and middle racks, swapping positions halfway through.)
Place meatloaves on one side of a baking sheet; roast on top rack for 10 minutes. Carefully add broccoli or green beans to empty side of sheet. Return to top rack and roast until meatloaves are cooked through and veggies are tender, 12-15 minutes more for broccoli or 10-12 minutes more for green beans.