Cut the chicken breasts into 1-inch cubes and place them in a large bowl.
In a separate bowl, whisk together the olive oil, soy sauce, honey, lemon juice, minced garlic, cumin, smoked paprika, salt, black pepper, and red pepper flakes (if using).
Pour the marinade over the chicken cubes and toss to coat evenly. Cover the bowl with plastic wrap and refrigerate for at least 1 hour, or up to 4 hours for more flavor.
If using wooden skewers, soak them in water for at least 30 minutes to prevent burning.
Preheat your grill to medium-high heat.
Thread the marinated chicken cubes onto the skewers, leaving a little space between each piece for even cooking.
Place the skewers on the grill and cook for about 10-12 minutes, turning occasionally, until the chicken is cooked through and has nice grill marks. The internal temperature should reach 165°F.
Remove the skewers from the grill and let them rest for a few minutes before serving.