I find it tricky trying to repair a hole on my CX tyres with a string.

I think its a combination of a lack of tyre height & volume. The tyre seems to deflate real quick and/or the prong with the string on it bottoms out on the inside of the rim internally before the string can penetrate the tyre.

Easier to do at home with the tyre removed, but trailside i’ve had a nightmare.

Just me or any tips???

Could try making the hole a little bigger so the string is pushed in easier.
I didn’t have too much of the problem the time I had to do it trail side but the tires were 40mm so probably bigger volume than yours.

String?

String?

Patch on the inside of the tyre. SOP for road tubeless tyre repair.

Oh? How big are these?
I just use rubber bands, they work well on the bead.
For a permanent fix, I pull the tyre & tie a knot on the inside & pull it into the hole. Adding a dab of tyre cement as well.