I always make one block to test....

No matter how good I am at reading a pattern, I still, always make a sample of a block/s using the directions in the pattern so I absolutely know my work is good and there are no mistakes or I can make corrections if needed.
peace

Gotta love having EQ. Or graph paper. Much easier to check for errors, at least on sizes cut. Directions are another matter.
I take at least a day to review all the directions before even making the trial block. Or so it seems.

I'm a visual learner; love youtube. It takes several re-readings for me to understand written directions sometimes and even then I'm not always sure of what I'm doing. So I wouldn't know a mistake in the pattern just by reading it. I would only think that I screwed up somehow. So for me it can be very frustrating trying to follow a pattern; therefore, I tend to do the MSQC video projects or like type video projects. I like Swoon patterns because they will have a video to watch of the project sometimes.

Were the seam allowances added to pattern or did you have to add them?

It was a paper pieced pattern with seam allowances included.

was the scale on your printer set at 100% when you printed the pattern?
That, of course, could be a problem......luckily, mine remains at that % all the time.......
I do a lot of PPing patterns from the internet.

When the pattern said 10.5" block, did it say finished size? Some times as someone else has said you might find a key or small print that tells you to enlarge pattern when printing, but it also may say to allow for seam allowance too. A lot of times they will print something up without showing room for a seam allowance.

It's not just free ones that goof up. I am working on one now that is a kit and it said to cut 6 of a size and I did and goofed on another piece and used the extra to correct a error I made and then sure enough the actual directions called for 11 of the one I used. Now have to get creative and do something else.

I've actually tried to write out directions - and it's so easy to miss something basic, or leave something important out. Only way to make sure they work is to have someone else try to follow them. Of course, it's the same for writing up any type of procedures. I find it often works best to have one person performing the work while another is writing down the steps needed - and then have a third person try to follow them.

If I'm paying for something, I hope the writer/developer took the extra time to troubleshoot the directions - if they are free, then I go with the flow and try to check through and count up and double check it all myself.