Trim the chicken thighs if needed and place them in a gallon size plastic bag.

Use a microplane grater or zester to zest the lemon and the orange into a bowl. Then squeeze the juice from the lemon and orange into the bowl.

Add the balsamic vinegar, honey, kosher salt, pepper, and crushed red pepper flakes into the bowl. Whisk until combined.

Remove 1/4 cup of the marinade and store in a covered container in the fridge. Pour the remaining marinade into the bag with the chicken.

Note: You can add a few of the lemon and orange wedges that were squeezed to the bag if desired.

Massage the bag until the chicken is evenly coated. Marinate in the fridge overnight.

Put the chicken into a casserole dish, sprinkle more kosher salt, pepper, and crushed red pepper flakes over top. Bake in a 400 degree oven for 30 minutes.

As the chicken is baking, put the orange marmalade and the reserved marinade that was set aside earlier into a saucepan. Bring to a boil and reduce heat to simmer 3 to 4 minutes, stirring a few times.

Brush the glaze over top of the chicken and bake in the 400 degree oven for 15 more minutes. Check to make sure the chicken is above 165 degrees and serve.