Here's a rig i used to use a few years ago, it emulated a running rig as well as a semi fixed bolt rig.
The hooklink was 10 inches long, tied in the normal knotless knot style with a loop at the end.
Which was then pulled through a uni link swivel, and the loop was pulled over the hook.
I used to pull the loop end near to the hook and then tie on two small bits of pva tape or string, shortening the hooklink by half.
The idea was the pva would melt in the water leaving the hooklink to travel up its own length on a take (emulating a running rig) and then jolt in the hook when the hooklink was straightened out.
The lead was usually a semi fixed heavy inline lead, great for pva bag work.
It used to work a treat but now i much prefer the early indication of a full blown running rig set up, plus im using pva sticks now.