Visible Embryo Carnegie Stage 18
Visible Embryo Carnegie Stage 19
Visible Embryo Carnegie Stage 22
From this website it seems to me that first bones are made and then muscle, then as bones develop in turn the muscle develops.
If what you are taking to be flesh is cellular material then even bones begin in this way. Rather they are first very similar to any other types of cells, they go on to become cartilage and then harden to become bone.