Using a sharp knife or peeler, remove the skin from the jicama. Cut the jicama in half once, and then each half crosswise into half moon—shaped slices. Dust with the chile powder and set aside.
Rinse and pat dry the scallops. Slide 5-6 onto each metal skewer or wooden skewers soaked in water for 30 minutes. Sprinkle with salt and pepper.
Preheat your Spark to 500°F and rub your grates with oil.
Prep your extra toppings to bring to the table, and smash your avocados in a bowl.
Place the jicama on the grates and close the lid. Cook for about 10 minutes then flip. After about 5 minutes add the scallops to the grill. Close the lids. Cook for about 5 minutes or until they release from the grill grates. Turn over and cook for another few minutes until fully opaque. Remove the scallops and the jicama from the grill.
Heat your tortillas in the oven or microwave in a damp dish towel until warm. Meanwhile, slice the jicama into spears.
Bring everything to the table for each person to assemble their own tacos. Spread avocado on the tortillas, then top with jicama, scallops, and all other desired toppings. Finish with a squeeze of fresh lime and pinch of sea salt.