A very simple and easy to make fly...
I have several versions of this fly, some made out of foam, others from synthetic fibres, but the one I like best and find most successful is this version tied from natural bucktail. Bucktail absorbs water and sinks, the finer hairs at the tip of the tail sinking faster than the coarse fibres from the tail base. Using coarse fibres and careful use of floatant will make you a fly that will float for a minute or two then slowly sink at the same rate that real bread will 
Start with a Kamasan B900c Size #4 Crab Hook. These are very fine and sharp hooks, but quite strong. They're designed for use with crab baits but the wide gape lends itself well to fly tying. Tie on white silk and build up a body all way to the bend of the hook, winding several layers and finishing with your thread at the bend.
Take a thick pinch of white bucktail and tie it in at the end of the hook, allowing it to spread around the shank of the hook and to flare out as the thread is tightened. There's no need to be that neat with the bucktail as it's going to be trimmed back later.
Keep adding pinches of bucktail and tying them in until the whole hook shank is covered.
Tie a whip finish behind the eye and add a spot of varnish to seal the threads. The next stage is the 'artistic' one - trim the bucktail until it's a rough square/rectangle shape (mine are about 15mm x 15mm in size and only about 5mm thick). You can use a permanent brown marker to colour one edge to make it look like bread crust but I don't bother as when I'm fishing I give my crusts to the dog and only scatter white bread to attract the Mullet
P.S. If you get tired if missing bites you can expose the hook point a little more or just return the fly to your case, put it down to experience, and squeeze a flake of real bread on a hook instead 
