use a crochet hook to tie a perfection loop
Many times I wish to tie as small a perfection loop as possible on my leader to fly line connection if I the line can't support a nail knot. Or for my tippet connection to the butt. Cuts down on bulk and wind resistance. What I do is use a size 4 crochet hook. Form your two loops as small as possible - much too small to manipulate the second loop through the first loop in the conventional manner - then pass the hook through the first loop, hook the second loop and pull it through. Use the shaft of the hook into the final loop to snug up the knot.