This is a little trick i learn in a high end professional kitchen in Sydney a few years ago and i have used ever since with chicken, duck and fish.
I will use boneless chicken thigh fillets for the example below but it works the same for all meats with skin that you want crispy (except for pork belly and shoulder which need longer cooking).
Lightly oil and salt the skin of the chicken thighs then place (not crowded) into a cold non-stick pan. This is important. The pan must be cold when you start the cooking process as it stops the meat tightening fast and allows the all areas of the skin to touch the surface and get crispy! Right then, now turn on the heat to medium.
Cook skin side down moving the pieces of chicken around just a little every few minutes to ensure they don’t stick. After around 10-12 minutes you can turn the heat up a couple of notches to a medium-high heat) and continue to cook skin side down until a deep golden brown.
You will notice the chicken will be cooked 3/4’s of the way through from the one side so once it is beautifully golden brown flip over and cook for no more than a couple of minutes to just cook through.
Allow to rest for 5 minutes before serving.
When applying this method to thin fish fillets such as snapper etc you will need to turn up the heat at 5 minutes and only cook for 1 minute once turned. Enjoy!