Unless the pieces are uniform in size, this is actually quite hard. Given a chicken breast thickness also varies, getting uniform size is actually difficult. Some people will suggest hammering it down. This would work but extra effort. Also smaller pieces = larger surface area = easier to dry out.

Personally I like to pan roast them whole, preferably using skin on breast. The slice/cube and add to whatever I am making.

Heat oven to approx 200C. Marinade in any seasonings you like to the breast. If its wet dry off before cooking. You can reserve marinade to add back later. Heat a pan to hot. Add oil, add breast skin side down. Pan fry until nicely brown and rendered. Flip. Add reserved marinade if using. Chuck it in the oven and cook till internal temp at thickest part is 70C. Take out of oven and let stand for 10mins. Eat.