I assume that want to attach e.g. a MeshRenderer to the BoneFollower component and have the original skeleton Mesh split at the draw-order location of the bone (the bone's slot), and your follower-mesh rendered in-between. By default, the generated skeleton Mesh is not split.
To split the skeleton Mesh at a certain slot, there is the SkeletonRenderSeparator component provided with the spine-unity runtime. See the spine-unity documentation section below for details and the provided example scene:
https://esotericsoftware.com/spine-unity#SkeletonRenderSeparator
