How would you join two dyneema cords together?

Let me put the OP's question to a particular scenario. Let's say I have to build rappel anchors on boulders to retreat or descend from a long multi pitch route. The only "webbing" I have is 60 cm Dyneema slings like the ones in the picture.

The slings aren't long enough to wrap the boulder or constriction where I want to create the rap anchor.

Is there a safe (and reasonably simple) way to cut some of these slings and tie them together to create a longer piece of Dyneema?

If I ever were in this situation, I would probably girth hitch multiple slings together (without cutting them). However, because every sling is doubled up, that would use up my supply of slings twice as fast. Maybe there is a better way.

I would use a water knot backed up by triple fishermen's, but once you do that you'll probably end up with shorter segments than if you had just girth hitched!

As Greg noted above... Splicing a loop and clipping with carabiner.

youtube.com/watch?v=d0B6tYT…

Morgan Patterson wrote:As Greg noted above... Splicing a loop and clipping with carabiner. youtube.com/watch?v=d0B6tYT…

That's not something I see myself doing on a tiny ledge while retreating from a storm.

C. Archibald wrote: That's not something I see myself doing on a tiny ledge while retreating from a storm.

Wasnt responding to you... This would be something you would do at home before your climb to make a rabbit ear sling.

And you're talking about a sling that is pre-sewn, and I'm talking about a piece of Dyneema cord as referenced in the OP. And without compromising the dyneema, you would splice a loop...

Morgan Patterson wrote: Wasnt responding to you... This would be something you would do at home before your climb to make a rabbit ear sling.

Ah, gotcha.

Just to be clear, any knot cuts rope strength a lot. Bowline, figure 8, double fishermans all cut rope strength by 40-60% depending on rope type. Failure is in the knot most of the time. A splice cuts rope strength by 0-20% and failure is in the unspliced rope most of the time. The splice effectively doubles the rope over the distance of the splice. The rough rule of thumb I use is a knot is 50% of rope strength; a splice is 95%.

This article shows rope tests for different knots and a splice:
neropes.com/Resources/sail_…

I understand sewn tape loops are close to the strength of the tape, where knotted tape loops have similar strength loss (50%) but I haven't seen a good reference; anyone?

electricant.net/projects/te…
I sew my own slings, dogbones, PASes, and occasionally belay loops. I use B92 (size 16) polyester UV protected thread (outdoor upholstery). It has a tensile strength of approximately 14-15lbs, and each stitch is doubled up (but I figure it loses 50% of its strength in the stitch since its two threads interlocked like >80% of the original strength.)
For 5/8" tubular webbing this is around 140 stitches + safety margin = 200 stitches.
Failures tend to be where the webbing meets the stitch field. The stitches don't fail since they're stronger than the webbing.
I don't bar tack since I don't own a bar tack machine. A zig zag of straight stitches on the stitch field works just fine and most home machines will do this.