I'd like to know how to make a stereogram mask using Inkscape.
Can you please modify the flat color to give it the depth it takes for a stereogram mask?

You can check how the depth looks as a mask, here:
https://yx.stereogram-maker.com/
And then the mask gets uploaded, here: any stock pattern will suffice.
https://www.easystereogrambuilder.com/
 

I learned how to make a mask with Inkscape. Layer a photo underneath the design, like so:


https://yx.stereogram-maker.com/