Line a 6-quart slow cooker with a parchment sheet, spread the bottom evenly with the 4 oz (113g) of sliced lemon, then place the 32 oz (907g) salmon fillet on top and drizzle with 1 tbsp. (14g / 0.49 oz) of the avocado oil.
Stir together the 1 tsp. (3g / 0.11 oz) garlic powder, 1. 5 tsp. (9g / 0.32 oz) salt, 1 tsp. (2g / 0.07 oz) black pepper, 0. 5 tsp. (1g / 0.04 oz) red chili powder, 1 tsp. (1g / 0.04 oz) Italian seasoning, and the remaining 1 tbsp. (14g / 0.49 oz) avocado oil in a small bowl until combined, then thoroughly rub this mixture all over the top of the salmon.
Pour the 3 tbsp. (45g / 1.59 oz) lemon juice and 1 cup (240g / 8.5 oz) chicken broth around the base of the fish (avoid pouring directly over the seasoning) and secure the lid.
Plug in the slow cooker and cook on the low heat setting for exactly 2 hours.
Meanwhile, as the slow cooker finishes, preheat your oven to 400 degrees F (200°C).
Once the fish is done, carefully lift the inner pot out of the slow cooker, place it directly into the preheated oven, and bake for 5 to 8 minutes, or until the top of the salmon is nicely browned.
Lift the fish out of the pot using the edges of the parchment sheet and set it aside to keep warm.
Transfer the remaining hot juices from the slow cooker pot into a medium skillet pan and place it over medium-high heat on the stove.
Bring the cooking juices to a boil and let cook for 1 minute to slightly reduce.
Turn the heat down to a low level, then whisk in the 0. 25 cups (60g / 2.12 oz) heavy cream, 0. 125 tsp. (0. 5g / 0.18 oz) lemon zest, and 0. 25 cups (22g / 0.78 oz) grated parmesan cheese.
Cut the resting salmon into 6 equal portions, top each piece generously with the creamy lemon sauce, garnish with the 2 tbsp. (8g / 0.28 oz) chopped parsley, and serve immediately.
Dry the Salmon Completely: Before rubbing the spices and avocado oil onto the 32 oz (907g) salmon fillet, pat it completely dry with paper towels. Removing excess moisture ensures the spices adhere properly and helps the fish firm up beautifully during the slow cooking process.
Don't Skip the Oven Finish: Slow cookers are incredible for locking in moisture, but they don't provide a crust.
Transferring the inner pot to a 400-degree F oven for those final 5 to 8 minutes is the secret to getting a restaurant-quality, slightly caramelized top on your Salmon with Creamy Lemon Sauce.