I would not bother sewing onto a muslin backing for strips that wide. Have made many log cabin blocks in different sizes and simply strip-pieced them without a muslin foundation. Muslin adds a surprising amount of weight.

Never used muslin backing for any log cabin quilt blocks, Just make sure you have a 1/4 inch foot to get accurate seams.

sometime people "iron" instead of "press". therefore, the pieces become stretched. which is actually quite easy to do with narrow strips. if you feel you might need to use a foundation, try light-weight interfacing, but even that will add weight to the quilt.

I could see using foundation piecing where the logs of the cabin are skinny, but not for a 3" strip. I did not use foundation on my Log Cabin and did fine. Starching the fabric would help for stability.

My method varied from the instructions in that I did not do string piecing. Instead, I finished one block at a time. (String-piecing got me confused)

the muslin is simply a foundation, helps keep everything square, a bit easier to work with. if using scraps sometimes they are off grain and stretchy, a foundation will help, and muslin doesn't have to be removed like paper does it just remains part of the quilt.

I have not used foundation. My advice is to make sure each piece you sew on is squared this will prevent wonky blocks! See my avatar I know!

I've never used muslin or any backing ...I've done PP but usually just piece a LC as any other block

Thanks for all your suggestions!

I've never done that with log cabin, only when I'm making a string quilt.

I have made a log cabin quilt piecing it on muslin and my advice is to use the paper another suggested, or go for it without paper. It did make it stiffer, less appealing to snuggle with. How many times will you be "going around the hearth" so to speak? The more times around, the more risk for distortion, but with your width strips, there should be enough fabric for squaring up frequently. Good luck and don't forget to post photos!