Combine avocado, red onion, lime juice, and salt in a medium bowl. Mash avocado with the back of a fork to break up some of the pieces but leaving most of them in hunks. Gently fold in herbs. Taste and add more lime juice or salt if needed. 

Press a piece of plastic wrap directly onto the guacamole. Cover bowl tightly with another piece of plastic wrap. Refrigerate until ready to serve. 

Remove any pin bones from the salmon with kitchen pliers and place fish on a large baking sheet. 

Combine sugar, oil, salt, chipotle chili flakes, ancho chili powder, garlic, lime juice, oregano, and black pepper in a medium bowl. Stir to combine. Spoon marinade over fish, set aside while you prepare the grill. 

Empty any ashes from the bottom of the grill and open the top and bottom vents. Pour Kingsford charcoal into grill and light. You want to cover at least 3/4 of the bottom of the grill with charcoal so the entire side of salmon cooks evenly.  

Place grill grates over the lit charcoal to preheat them. Once coals are covered with gray ash, use a grill brush to clean the grates. 

Soak a paper towel with a couple tablespoons of canola oil and using a long pair of tongs, wipe grates with oil. 

Place salmon, meat-side down (skin-side up) on grill. Grill, undisturbed for 5 minutes. Using two long, metal spatulas, carefully flip fish over and cook other side another 5 minutes or until opaque and firm to the touch. 

Transfer to a large serving platter, top with guacamole and serve.