Hi mate. Heres how I do it:
You need to tie a sliding stop knot above the float with either thick mono, elastic band or powergum, or even use a length of thin silicone tube with the line threaded back through again like you might use on a baitstop for clipdown rigs. Quite a few ways to do it....
... then a bead to push up against the stopknot,
then the float
then a swivel.
18 inches or so of line
the right weight to cock the float
then a bead to protect the knot from the weight
and further swivel
then the same or slighly shorter hooklength as your first length of line.
Personally I use lighter bs hooklength than mainline so you will only lose the hook should you get snagged.
Being careful with these 2 lengths and keeping the hooklength shorter than the first with the 2 swivel arrangement will prevent tangles when you cast.
You adjust the depth by sliding the stopknot up the mainline. I usually tie the knot last. 12 feet is usually a good starting point
Make sure the rod you are using has wide enough eyes to allow the free passage of the stop knot or silicone slider when u cast and retreive
Tight lines bud.