Or site the obelisk after planting :-)

The good news is that broken stems are not the end of the world with clems. They should recover rapidly and start pushing new growth if provided with normal care.

It is a type 3 (hard prune) so it will bloom on new growth from this year if it is a large enough plant. If it is small, it will benefit from the unintended pruning and fill out more than if you hadn't pruned it. If you haven't clipped off any broken stems, do it now.

Don't worry about the stems! You unintentionally just caused it to put out more growth. It will recover!

If you want to try for more of the same plant, try to root those broken stems (with the appropriate branches chosen for cuttings)

There are specific techniques for rooting Clematis cuttings so read up on it first. It is not the same as most shrub cuttings.