Using large beads and fishing wire.

The triangles could be large pieces of plastic with holes put though them for the string to go through, while the large circles are flat round beads.
By using one long strand of fishing wire, you can string the triangles to the circles one at a time, alternating between the two until you reach your desired length. then string it though a hook of some sort before going into the opposite direction, putting in new triangle pieces while going though the same circle piece before stringing to the opposite end of the hook and turning back.
Continue until you get the desired height of your collar, and you'll get a home made, easy to wash collar.