bearisgray

I would was h the fabrics - especially for something like pillowcases - because fabrics do not shrink evenly.

The finished pillowcases will wash up and fold better if most of the shrinkage has been removed before making them.

If you are using only one fabric for each pillowcase, do whatever. But if you are making pillowcases with the contrasting cuff and trim, I strongly recommend washing/shrinking the fabrics before assembling them because if the possibility of uneven shrinkage.