How to read the slash in a “ 1/1 plain weave” or “1/4 satin”?

Is it pronounced as one-by-one or as one-to-one when read out?

Please note that this use is related to the binding structure of textiles.

Here is an example of usage from Role of Yarn Tension in Weaving by Samir Kumar Neogi (©2016):

It is observed that when the weave is changed from 4 / 1 satin to 1 / 4 satin， the average warp tensions at shedding and beaten-up increase (Fig. 7 ．38A ）

It is best to use what the slash is normally used for which is fractions or more specifically ratios. The sentence can be read as "the weave is changed from 'four to one' satin to 'one to four' satin". The ratio of A to B is what the text is about. The slash has just been used as shorthand.

This sounds like a ratio of one-to-one or one-to-four or whatever. In plain textual writing, I'd write it out that way. If it's technical writing, the slash construction is fine, as long as that's what the particular industry conventionally does. Beware, though, of using technical contractions like that in "standard" writing for ordinary civilians and normal people.