I do not have any flashers here at the house, all up at the shop. However I just do it pretty basic to the ones you can buy pre-made. I use two different set-ups. I either go Flasher straight to a 3 way swivel- 18"-20" 20lb mono ldr for the weight and a 4'-5' 30lb flor ldr for the crankbait. OR I will put a slider on my line and drop a 18"-20" 20lb mono ldr for the weight, then tie to the flasher then go 4'-5' 30lb flor ldr to crankbait. Here is something to kinda use as a reference for the slider rig,
http://www.pcsportfishing.com/blog/75 I do mine just a little different. I would put my bait closer to the flasher if i was using a swimbait or even live bait. With the crankbait though, I found you want a little longer leader to allow it to put of its true action. If you use a 8'-10' diving saltwater rapala, you will feel it dig from time to time and bounce off the bottom. If you go with a 4'-6' rapala, it will however just above the bottom. I like to dig my bait into the bottom, go a few feet past the point, then pause it for a minute. Then continue on.
Be sure and play with your crankbait a little on a bass rod before you rig it up. A lot of crankbaits I have thrown need tweaking for the saltwater. I dunno if its bc of the density difference or what, but they run different in freshwater than saltwater. Note, this is all my personal opinion, experiences, and preferences. You can always play with it a find something that works just a little bit better.