They are very delicate, the first 2-3 are the hardest to assemble without breaking. Once you get those together with your hands, place them on a flat surface.
The initial assembled links are held in place with a bass wood plank while links are added with a second plank (small file, c-below) pushed at a slight angle till they click into place.
Push down with some force on the assembled links while offering up the new ones....my bass wood plank is tall enough to allow pressure on the links without touching the fragile guide horns.
The rest of the links are pushed into the assembled ones at an angle using a second bass wood plank all while laying perfectly flat on the table.
If you break a few you'll find usually only one horn will be broken, these can be hidden behind road wheels etc. Of course you'll need to count off the tracks to know exactly where to insert the broken link as not to be seen.
I may have some pics of my special tools I use....
Edit.....forgot to mention only working in short 5-6 track runs, these larger runs are easier to force into each other once all tracks are finished.
Edit....AGAIN, found my pic of the process....you can see the tall bass wood plank holding the completed run tight to the table. My memory is fading though...I used a small file to force the links into the run not another bass wood plank!