It’s usually better to have as clean of a URL as possible. And for that reason, in most cases, I would not add /blog/ to your URLs. If you are really trying to rank your website for the keyword “blog”, then this might be an acceptable practice to add /blog/ to your URLs. Allowing the blog posts to have cleaner URLs without the directory could incentivize users to write more. It could also allow you to have a higher click-through rate on Google.
I specialize in Organic Search Promotion for B2B Tech Companies. Currently, I'm working as a Digital CMO / Chief Content Officer for a B2B IT company Belitsoft. I'v been building a high-performing team that delivers positive ROMI through the creation of Lead generation Content visible to Google.