To be honest it’s not worth the bother now, several companies make them ready made, I particularly like the Preston versions which come in various sizes to suit elastic size but I have to admit I use my own Dacron as I find the ones supplied a little too short for my liking but got to have the sleeves. Dacron is cheap to buy from any tackle shop carrying a good selection of specimen carp tackle.

the Drennan dacron connectors are very good.

You need a loop of dacron & a tail rubber from any carp lead set up. Tie a single overhand knot in the elastic. Make a loop of dacron & tie off in a double overhand knot. Pass the dacron loop over the elastic , behind the knot in the elastic, & pass the dacron knot through the dacron loop. Tighten the dacron & then pull the dacron knot through the tail rubber, until the loop is fully protruding through the narrow end of the tail rubber. The elastic should now be trapped in the tail rubber with the dacron protruding. Trim the elastic off behind wide end of the tail rubber & you’re done.
Regards Peter.

look up carpin kev on ebay, he makes brilliant dacrons 5 for £2.25 all sizes good quality, never let me down.

You can get many uses out of one connector though

30lb flyline backing. I use helicopter beads. To create a stiff boom from the dacron, twizzle them at either end in opposite directions.