Simple command line for making the META file
apt-get install flvtool2
Also you should add in the "g-" into your ffmpeg scripts. Here is an example
flvtool2 -U <video_file>.flv
In ffmpeg the number of keyframes is controlled by the g- flag. A smaller value leads to more keyframes and a larger file size. With small video files (less than 10Mb) a value such as 30 should be fine.
ffmpeg -i UncompressedMov.mov -sameq -g 1 OutputFile.flv