You can just put a small barrel swivel between your main line and your mono line to your spoon and run a little tag line off the barrel swivel for your fly.You can tie your fly off first with a palomar knot and leave enough line for your spoon but I think the barrel swivel is the best way ,on ice with cold fingers ,I look for the easy way.
It has worked well for me and you might be surprised how many fish will take the fly
Good luck
Gary