I wonder if a sloppily filleted chicken breast will yield a drier, less flavorful chicken. If it does, why is this the case? And what is the proper way to filet a chicken?
The way meat is cut can affect it in a few ways. The most obvious is cooking time, a thinner cut of meat with more surface area will cook much more quickly than a thicker cut with less or equal surface area. Thus unevenly cut meat will cook unevenly, with thicker portions remaining raw while thinner portions are cooked through or overcooked. The way the meat is cut can also affect how well spices will stick to the surface of the meat, where again a higher surface area will lead to more spices sticking. This can be further increased by cutting the chicken in a jagged manner, which provides more area for spices or rubs to stick. The way it is cut can be especially important with chicken as it tends to cook and dry out very quickly, and so an unevenly filleted chicken breast will become very dry in areas while possibly remaining unsafe to eat in others. Thus, rather than cutting the chicken in a jagged manner to get spices to stick better, it is generally a better idea to make shallow cuts in the surface of the chicken breast and place seasoning or whatever you like inside (you have likely seen this before, called hasselback chicken, though it is more commonly done with steak), as the jagged cuts lead to differing thickness across the cutlet. Ideally when filleting a chicken breast you would make a single cut resulting in two evenly sized pieces of meat, then if you would like more surface area for your seasoning to take hold make shallow cuts across the grain of the meat. Here is a website that goes more in-depth on the proper method for fileting a chicken breast into cutlets.