Technique for shaping meat for cordon blue (alike)
I would think this would be a great application for boneless, skinless thighs. I've never had much luck trying to get uniform pieces boning dark meat myself. Done commercially though, they're usually fairly regular. Trim off any excess fat and gently pound them out to about 1/3 inch (2/3 centimeter) between pieces of plastic wrap (don't use the jagged toothed side of a mallet, use the flat side or something smooth like the bottom of a pan). Place your filling on the chicken piece, add any "wrapping" (bacon, or ham slices or whatever). Just using one of the sheets of plastic you used for the pounding, tightly roll up the chicken with any filling and/or wrapping you desire, twisting the plastic wrap at the ends to get the tightest possible "cigar". If you want to use bacon to wrap, but your slices aren't long enough, overlap two slices at the ends and give them them a bit of a pound where the slices overlap. Chilling the roll should help keep the slices together, but you may need to tie them with twine. Chill for at least a couple of hours. After chilling, remove the plastic wrap and secure the rolls with a toothpick or twine, bread if desired. I would consider baking the rolls, seam side down on an oiled sheet pan instead of frying. If you end up "splicing" slices of bacon, try to keep the seam of the bacon lined up with the seam on the chicken. That way, baking seam side down will help keep both seams closed.