Remove the membrane from the back of the rack (grab it with a paper towel and pull firmly). Pat the ribs dry, then cut rack into 4 pieces.
Make the spice rub by mixing together coconut sugar, paprika, garlic salt, and black pepper.
Rub generously all over both sides of all rib sections.
Wrap each rib section tightly in foil. Place on a baking sheet and bake at 275°F for 2 hours and 15 minutes.
Make the cucumber salad. Toss sliced cucumbers with soy sauce, rice vinegar, maple syrup, chili flakes, and sesame oil. Let marinate for at least 10 minutes.
About 20 minutes before the ribs are done, combine all glaze ingredients (coconut sugar, soy sauce, rice vinegar, sesame oil, grated garlic, red pepper flakes) in a small saucepan over medium heat.
Simmer for 5 minutes, stirring frequently, until slightly thickened.
Carefully unwrap the ribs. Transfer to a preheated grill over medium-high heat (or place under the broiler). Brush generously with glaze and cook 3–4 minutes per side, glazing again each turn, until sticky and caramelized.
Serve. Slice the ribs between the bones and serve immediately with the cucumber salad and steamed rice.