I take about 10" of braided mono, as per Juro, 30 or 50 lbs depending on the flyline size. Singe each end to stop it fraying. Double one end over to make a loop of the size you want (you may need a much longer piece if you are making a big loop for the running line end of a shooting head to allow you you change heads quickly on stream).
Take a doubled length of single strand leader wire & push it into the side of the longer leg of the loop (towards the end of the loop), bringing it out of the side after about 1/4 inch. Thread the end of the shorter leg through the wire & pull it through.
Now do the same again, but pulling the longer leg through the shorter one.
Repeat one more time, pulling the shorter leg into the longer one, tucking the end inside the longer leg.
You now have a flexible loop (no stiff glue section) that cannot pull out.
I attatch this to the line by slinkying the line into the leftover braid (I like to have about 4-5" left for the overlap) & then tie three separate 10 turn nail knots with 6lb test mono at the far end of the braid.
I use this system for both ends of all my lines & have never had one fail, including my best striper, 42" brought back against an outgoing tide.