Splicing your own rope is fun and productive. There’s a wide variety of splicing tools available online, but I prefer a simple DIY solution.
The polymorph used in the video is available in bulk through many online retailers. If you just want a small amount for specific projects you can buy it by the ounce in my shop.

Polymorph
Polymorph is play dough for grown-ups. It’s a thermoplastic with a melting point of 140 °F (60 °C) which makes it easy to melt in a pot of hot water and mold into any shape you want. Use it for making handles on spicing wire or anything else you can imagine.
Sold by the ounce, which is about 3 tablespoons of pellet…
$1.50