I've looked through many similar questions, but haven't yet been able to find a solution to my particular problem. It seems fairly straight-forward, but I can't seem to find the correct combination of settings to fit my desired structure. I would like my (standard) posts to have a URL of mysite.com/blog/postname. I then have a couple of category archives that I would like to have a URL of mysite.com/blog/categoryname.
In the Permalinks menu, setting a custom structure of /blog/%postname%/ generates the correct URLs for the single post view, but sets a URL of mysite.com/blog/category/categoryname for the archive. Using a plugin like Yoast to remove /category/ from the URL generates the correct link to the category page in the WP-provided navigation (mysite.com/blog/categoryname), but seems to ultimately redirect to mysite.com/categoryname.
I've also tried different combinations like setting blog in both the custom structure and the category base. This generates the correct links in WP-nav and to the category archives, but ultimately results in a 404 for the single posts.
It seems like I'm overlooking something simple, so I would appreciate it if anyone could point me in the correct direction. Thanks!