Hi Mel, Your question is rather implementation/logic one, so you may consider asking it in a different forum.
As far as I know, JKFF are mainly used in a latch/shift registers. Moreover, I think that JKFF building blocks is actual DFF. In other words, use a DFF instead of JKFF. Building a simple one shot pulse generator from DFF should be easy. For example http://www.hqew.net/circuit-diagram/DhttpdFLIPhttpfFLOP-OSCILLATORS_13142.html
