Use strong and reliable double-sided tape to avoid moving template on the surface.
When used with 17mm bush guide and 1/4"(6.35mm) router bit, you don't have to worry about chiseling - bow will match perfect to the routed space.
Draw a shape of your insert on the material and use a jigsaw to cut it out leaving 2mm excess.
Use double-sided tape to attach bow template to the material and flush it to the correct size - it will match perfect and tight without chiseling.
