The word has even been used by a few published authors, probably the best-known being Gerard Manley Hopkins in his poem
"The Wreck of the Deutschland":
... in thy sight
Storm flakes were scroll-leaved flowers, lily showers—sweet heaven was astrew in them.
But then, he was the holder of a poetic licence - a couple of lines before that, he used "unchancelling".
Astrew is possibly a portmanteau word, like some of the words you coined in your post, ensiform. Maybe it is a combination of
strewn and
askew.
Keep using it, ensiform, and maybe one day it will find its way into the dictionaries.
