In a large bowl, add all ingredients for marinade and whisk until combined. Add chicken to the bowl, cover and refrigerate for a minimum of 4 hours.
Preheat oven to 425 degrees.
Pour chicken and marinade into a cast-iron skillet. Roast in oven for 30 minutes. Remove from oven and place on stove top. Turn on heat and bring to a simmer until sauce thickened, about 1 to 3 minutes.
In a large bowl, add red pepper flakes, sugar, salt, lime zest and juice, and coconut oil. Whisk until emulsified then add cilantro. Cut cucumbers and add to bowl along with mango and toss to combine.
Add chicken to a plate, top with sauce. Serve alongside cucumber salad.