The phrase "little indentation" means a small hollow or dip in a surface.
Sentences with «little indentation»
My crust looks so pretty because I pressed the Paleo Pie Crust dough up over the edges of the pie dish and then made little indentations with a fork. (elanaspantry.com)
As the batter cooks on the skillet the bubbles pop, leaving you with crepes with lots of little indentations and tiny holes. (willfrolicforfood.com)
Then, use your fingers to make little indentations all over the surface, like you're miming playing the piano. (andcuriously.net)