I am working on a watercolor grid wall hanging. Can anyone tell me if after I sew the one dirrection, do I nip any of the seams before I sew the other direction?
Also, it is a 2" sq. and if I want to make a 2"( 1/2 sq) what measurment of thefabric sq. Do I need to cut first so I will end up with a 2 " sq. Thank you for any help.

Yes, you would nip each intersection after you sewed all the seams in one direction. That way you will be able to offset the seams in opposing directions, and eliminate a lot of the bulk when you started sewing in the other directions.

The formula for HST blocks is the FINISHED size plus 7/8" for the two starting squares.

Are your solid blocks on the grid finishing at 2" - so you're actually putting down 2.5" squares of fabric?

Or are the solid squares 2", and finishing at 1.5"?

Either way, I would cut larger starting squares for the HST blocks, make the HST's, and then trim down to the exact UNFINISHED size required.

Thank you for your reply. My grid is one ", but I am making it a 2". So my sqs. are cut to be 2 " sqs. But on some of the flowers, I want to make it 2 colors, So if I want to end up with a 2" sq, what shoud I cut my fabric sq. to geta 2' sq. triangle. . I was thinking 2 1/2, but then I had to sq. all them up. Thank you for any advise. I am still learning about quilting, but I have found my love of it.

If you're cutting the solid squares to be 2" for placement on the grid before any sewing - right? - then in order to make a HST block to fit that, you need to start with two 2 3/8" squares.

That's the exact measurement.

But, like you suggest, I would start with bigger squares 2.5"+,
make the HST, and then trim them down to a perfect 2" HST block, ready to be fused to your grid.
And when you sew the lines on the grid, the diagonals should also be perfect.

Sounds like a fun project. I hope you'll post pictures.