When’s best to divide and move irises?

[HeadFairy]

I’ve got some that send up plenty of leaves every year but never flower, so I think they’d benefit from being divided, when is best to do that? And what’s the best position for them?

Late summer is supposed to be the best time. I think they like to be planted very shallow, and in free-draining soil. That's about as much as I know, maybe check the RHS website?

The rhizomes like to bake in the sun. Cut them into chunks and leave them half exposed. If there are leaves, cut them in half.

Thanks… I wonder if they’re too far back in a bed then, if they like to bake in the sun? I’ve got a very sunny bed but they’re at the back, and are probably a bit over shadowed. Thanks!