This necklace design is called a “many to one” necklace, meaning that part of the necklace has many strands and part has one strand.
The first time I saw one of these that was handcrafted, I asked the designer – how did you deal with all of those thread ends? I thought that each of the “many” strands was an individual thread that had to be terminated or knotted off in some fashion – and it’s hard to hide a whole lot of knots especially in the front of a necklace. She very generously explained that you cut the beading wire for the “one” pieces and crimp one end on each leaving a small loop. Then, using a long piece of beading thread, begin adding the “many” strands working back and forth from one of the small loops to the other. This leaves two ends which are then knotted between the beads, hidden, and secured with a drop of glue. The “one” sections are then completed in a complementary design.
I modify this slightly by taking a second long strand of beading thread and making sure I have done two passes through each of the “many” strands to make sure the necklace is strong enough. This gives me four ends to deal with rather than two, but with so many strands there are plenty of places to terminate them. I tie a short bit of string around each strand when I have done the second pass to make sure I get them all. I remove the strings when I am done.
I think the “many to one” technique is great and I have used it for bracelets as well. I think what’s even better is the willingness of so many in the arts and crafts community to share techniques and ideas with one another.