How to piece my blocks with mostly short seams
 

I have a quilt top with 25 blocks which I am sashing. I want to sew it together with only one long row. I'm hoping this will keep it straight. I have already started sewing 4 blocks together in each corner. I'm trying to attach a picture but it won't upload.

I've never sashed one long row. I was taught to sash as I joined the block. Both ways are always straight.

You most likely need to resize your photo so it is a much smaller file size. Most photo viewing programs have this capability.
Regarding sashing, it is challenging to sash the way you describe. The challenge is keeping the blocks lined up on either side of the long sashing strip. Use a ruler and mark the wrong side of the sashing where the blocks are already attached, marking the side of the sashing where the new row of blocks connect. Pin (a lot) or glue to keep them lined up as you piece it. I prefer to use cornerstones but there are situations where you want an uninterrupted sashing. Even in those cases I will often have seams in the sashing and sash the blocks as I go. Peckish posted a great example of how to do that a while back. Hopefully she sees this post and will repost her technique. If you still want a long sashing strip, take your time, mark and pin and you should be ok.

I guess you didn't like my columns in your earlier thread :p
https://www.quiltingboard.com/main-f...s-t307912.html

From what I understand you want and have, this is how I would do the blocks to have only one 5 block seam.

Wow! Thank you so much for taking the time to FTSE that diagram for me! You have some great advice for me! I'm amazed at people's willingness to help on this board! I think your idea will work so much better than rows!

I didn't even mean to start 2 threads on this topic. Lol.

Figured as much, happened (like now) I'm here drinking my coffee and was able to pounce.

Welcome to quilting and the board, glad to have you here and glad to help when I can.

If you do make one long sashing, I would recommend marking where the corners of the blocks should meet it, as if there are cornerstones there. This will keep your blocks in a straight line. It's the cornerstones in sashing that keep everything straight, and without them, marking where the imaginary cornerstones would be on the sashing is an important step.

I don't believe I have ever laid out sashing length way, always top to bottom with corner stones. It can be tricky but going slowly and with practice it fits.