Depending on the dimensions of the flames, I think a jigsaw is an excellent tool. Rotary tools, like the Dremel, also work very well, but require a lot more time and numerous bits. I prefer to use the Dremel sparingly -- for finish work and for hard to get to areas, where a jigsaw is impractical.
It would be a good idea to clamp the work piece to a scrap of plywood to prevent warping or bending while cutting.
No mater what you use, you will have to pay special attention to the finishing of the edges. Although a rotary tool has a lot of bits and attachments, I like using files of varying sizes and shapes. Finally, sandpaper to smooth the edge to a clean finish.
Grump, The Mad Modder