This is the tool to help you to tie FG knot with braided and mono leader.
With this tool, braid will be held with some tensions to make FG knot easily.
68g

You wrap braid to the two ends and shut the line holder to hold line. Then you put 20cm of mono leader to the center holder and shut it.
You twist the leader upper braid and lower braid in turn for 10 times.
Then remove 3 holders to make half hitches for 10 times.
At the end you make end knot and you are done.