My fabric scrap is too small to make the muff on it's own so my first step was figuring out how I was going to enlarge it. I decided to baste it onto a slightly larger piece of two layers of linen and cover the joins with some metallic gimp trim I have in my stash.
Close up of basting. It doesn't have to be neat to be effective!
I actually had about eight metallic trims which I considered and I find it interesting that one of the cheapest was actually the one that looked best...and most expensive...when paired with my fabric. It reminds me that it is best not to make assumptions about these things!
As to the fur lining, when I took the fur apart I discovered all sorts of interesting things. They had used huge sloppy stitches through the hide (but hidden under the hair) to hold various facings and turnings in place, and they had made the original vents at the hem with an integral, turn-back facing stiffened with something like soft parchment or a stiff lightweight leather. This gave a crisp edge to the fur while allowing it to cleanly continue to the reverse side. very nice. I was inspired by this technique to try making a facing strip of brown paper for the edges of my muff.
After cutting out my fur I split open a brown paper bag and cut out 3 strips of paper which were 2" wide. I marked one edge with a guideline 1/2" in and then basted it to the wrong side of the fur with the 1 1/2" edge hanging over
Then I flipped it back using the 1/2" of paper as a guide and basted it into place while also overcasting the cut edge of the fur
It makes a beautifully soft clean edge (with no shedding!) so I continued the same process on the other two cut edges of my fur. The third edge of the fur has a band of leather finishing the edge which I kept since I think it will provide a nice stable place to attach the buttons and will wear well.
Right side (but I think you knew that)
The facings give a lovely stiffness to the edge which I think will influence the finished muff to hold it's shape. After some consideration I decided that I wanted to add an internal layer of felt by basting it onto the front also. It helps fill in the hollow left where the front turnings end, and I hope it will keep my hands toasty.
Felt layer basted in place
The assembled muff
Next steps are to add more trim, sew the short ends closed, and add buttons and loops. Almost done.