No. I hold the leather at the edge of my work bench with my drawn pattern hanging off the edge. I hold the loose edge with one hand while I hold the exacto knife in the other, straight up and down, and with a gentle up and down motion, I cut along the lines of the pattern. It doesn't have to be perfect. After I glue the holster, I trim the edges with the same knife, and then sand them. It may be unconventional, but it works for me. I can't wrap my mind around how to use one of those round knives without wasting a lot of leather.
For belt slots, I cut the ends with a 3/16" hole punch. Then I draw lines from hole to hole, front and back, where the slot goes, and cut along the lines with the exacto knife. It is actually the only knife I use. I have even cut belt blanks out of double shoulders with it.