I have a 6X2-7/8" cone. How do I cut a piece of material to cover this?

Answer 1

Since you didn't specify, I will assume 6" tall with a 2-7/8" base.
The easiest way is to make a pattern by drawing a 6" radius semi circle on a piece of paper and cutting this out. Form the paper into a matching cone (center of circle at point) and slide over the cone, marking the point where the cut edge of the paper comes to in the wrap. Lay the paper out and draw a line from the mark to the center and cut on the line. There is your pattern. If you need seam allowance, you can cut 1/2" or whatever to the side of the line.