FlexTotem basically uses several of flexbar's buttons and uses them just for totems. So there are 4 buttons, one for earth, fire, water and air. When you mouse over these buttons it pops up with another bar with all of your actual totems. So mouse over and then you see like all of your totems you can cast. Once you cast one it then pops the hot key for that one totem in the buttons that are permanently shown that you would mouse over and it gives a timer and you can set it to a global or like the individual totem timer. Let me just link someone's screenshot of their UI using it and also a link to the flex totem webpage...
http://members.home.nl/wooz/FlexTotem/
Their webpage provides a fairly detailed explaination and also a few screenshots that are animated. Sorry I couldn't explain it too well it is kind of hard to explain lol. Anyways if we saw a discord version of that let me just say I would <3 forever lol. But anyways hope this answers your questions about it Loz.