Get a 16x9 frame made of steel. Place the frame in a very large dark room. Wrap it in some rags, secure the rags with copper wires (not nylon zipties. Use an accelerant that will produce the color of flame you wish.
Capture the footage, put it into AE, scale and position. add a feathered mask. Use any of several composite modes, probably screen.
Also, make sure you have at least one, trained fire safety professional on hand, for insurance purposes.
But rather than constructing it yourself, perhaps you should look into hiring a professional pyrotechnician; they can assure you the right look.
Alternatively, you could use stock footage such as this clip from Artbeats. Or, if you want more control, a multitude of clips and (using a layer blending mode such as screen, or add) composite them around your image.
There is also some excellent fire footage in Digital Juice's Compositor's Toolkits (both 1 and 2)
- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')
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