Key Ring Fob
This is a very simple weave. To tie the loop at the top I used
https://www.instructables.com/ABOK-783-Two-Strand-...
You can use any knot of your choosing.
Bring the left hand of your cord under to make a small bight.
Bring the working end (WE) under a and over b.
Bring WE over a, under b and over c.
Bring WE under a, over b, under c and over d.
The knot is complete.
Bring the WE back to the starting point and add extra plies as desired.