I fish the R Ure and occasionally the Ouse in Yorkshire, in places where the depth might be 12 to 15 ft deep.
I use a long cigar shaped sliding float threaded onto the line. Above the float there is a sliding stop knot tied on the line to set the depth. I thread a largish (20gm) drilled bullet on the line below the float, then tie on a link swivel. This set up leaves about 2inches of float sticking up out of the water when the float is carrying the full weight of the bullet.
I adjust the sliding knot so that the set up (float top to drilled bullet) is about 6 inches to a foot deeper than the swim. I cast out, let the float and bullet drift in towards the bank. The bullet scrapes along the bottom, then holds. Usually the current will partly submerge the float, but you can still see the float top. You may need to put the rod pointing nearly vertically upwards if you are fishing well out or the current is strong. I wouldn't let the float lay flat on the water because you may miss the initial stages of a pike taking the bait.
If the float sinks beneath the surface, reel in, slide the knot up the line, cast again and by trial and error you can get the right setting.
If the float is dragged right into the side by the current, it means you need to increase the weight of the bullet and put a larger float on.
There may come a point when a combination of depth and flow means that even a large weight float won't hold in the current. You then need to either fish close in to the bank or change to legering.
Technically, the system I use is laying on rather than legering.
You could replace the bullet with an bomb on a link swivel, when it would be legering.
I'm not sure that a proper leger rig makes much difference to the sensitivity of the rig. Pike seem quite willing to drag a large bullet and float behind them when they take a bait.
