Step 1: Set up your grill for direct grilling and preheat to high. Grill the empty planks until singed on both sides, 2 minutes per side. Let cool.
Step 2: Rinse the trout, inside and out, under cold running water, then blot dry, inside and out, with paper towels. Make 3 or 4 diagonal slashes to the bone in each side of the trout (this speeds up the cooking and allows for better absorption of the flavors). Generously season the trout inside and out with salt and pepper. Place a couple dill springs, lemon slices, and butter slices in the cavity of each trout.
Step 3: Tie bacon strips to the trout, one on top, one on the bottom. Arrange one trout on each plank, head to tail.
Step 4: Meanwhile set up your smoker following the manufacturer’s instructions and preheat to 300 degrees. Add the wood as specified by the manufacturer.
Step 5: Smoke the trout until the bacon is sizzling and crisp and the trout is cooked through (140 degrees in the center), about 30 minutes.
Step 6: Serve the trout on the plank, with lemon wedges for squeezing.