This plaid flannel shirt from L.L.Bean is a favorite of mine, especially at this time of year with its red, green, and ivory coloring! You'll probably be seeing it again at least one more time before Christmas. ;)
The majority of my flannel shirts are from L.L.Bean and Madewell. I find them to be the softest and thickest compared to other brands I've tried (looking at you, J.Crew Factory, and the soft cotton you claim to be flannel!). The L.L.Bean flannel shirts run bigger than Madewell flannel shirts; I bought size XS in all my flannel shirts but have been replacing my favorite Madewell shirts with size small since XS is just a bit too tight, especially after being washed. Some people recommend sizing down in L.L.Bean flannel shirts but since I have broad shoulders, my true size is fine. I prefer the "misses" sizing in the slightly fitted shirts for the longer sleeve length, but my first L.L.Bean flannel (last seen here) is "petite" sizing, which is great if you need shorter sleeves and/or a shorter torso length. (That flannel is also "relaxed", which makes it boxier than the slightly fitted shirts like the one shown here.)
The only downside to my more recent L.L.Bean flannel purchases is that it seems like they wear much faster than the shirts I purchased in seasons before; they get kind of a "nubby"/pilling texture on them after being washed and look worn because of that. I've read other reviews saying the same thing. I hope that they fix that soon! I didn't buy a shirt this season so I can't comment on if it's still happening. I've been babying the shirt I'm wearing here because I don't want it to look worn down!