can you cut off the black stems with the flower on it

Yes - cut the stems out at the base when the flowers are over.

Thanks for that
what if they are still in flower,
just that some of the stem are not upstraight
they tend to be lying over and look unsightly.

Rick.

You can cut them off as soon as they appear if you like, and certainly before they've finished flowering, it won't harm the plant. Might produce more, that's all.

Thank you very much for the answer to my question
regards flowering flax stems.

Rick.