I can help with the dog biscuit fly.
You will preferably need a wide gape hoow about size 10 and a lot of natural deer or elk hair.
Simply tie on the thread to the curve, and spin a lump of deer hair (i put a bulk of thread just behind the first lump to kick it out a bit more otherwise i have found my dog biscuits have tails lol).
Wrap through the butts of the hair towards the eye and spin another lump of deer hair (you should be about halfway) then i add a hi-vis post of antron or something similar so your fly is easily seen from any free offerings which happen to drift in to your swim

. Once the post is attached i spin two more lumps of deer hair and tie as small a head as i can get away with.
All that comes now i the messy bit of trimming.
If you are not exactly a purist (unlike me ofcourse always fish my dog biscuits upstream) carp tackle shops sell floating rubber dog biscuit imitations which make rather nice flies.
Dan