I threw together a fire elemental using a cheap marvel guy and a wooden base. This guy came in a pack of 8 marvel figures for $3, from Five Below.
Step 1: flock the base with gravel type flock and paint black.
Step 2: paint the flock white. This keeps the orange that’s going on next nice and bright.
Step 3: paint orange over the white. (Make sure the orange matches the figure.)
Step 4: clean up edges with black.
Step 5: drybrush black on the flock to make coals. Go kind of heavy with the drybrushing here, but make sure some orange remains visible.
Step 6: lightly drybrush light gray ashes onto the coals and around the edges where there is no orange
Step 7: glue the mini onto the base.
Looking back, one thing I might have done different is painting the bottom of his feet white before gluing. As it is, his feet look darker than the rest of him, because you can see the black paint through the feet.
This technique works great for all sorts of embers, as shown in the brazier below: