[The Fifth Horseman]

EoF: My trick for making animations in GIMP is to first save each frame as a separate file. Open the first frame, then open the rest as layers.
At this point it's best to save the animation as an XCF file if you need to go back and tweak something.
Convert image to indexed color mode, and run Filters -> Animation -> Optimize for GIF.
Now the only thing to do is adjust the timings between each frame - which is done in the Layers window.