I love using fill-in-the-blank stories to work on parts of speech. The problem I find with most of them is that they address too many different parts of speech in a single story. Friendship Soup is fun, winter story for practicing just naming singular and plural nouns.
If you are just introducing nouns, discuss what they are and come up with a list of them together. Then have the students fill in the story with words from the list. You can also have the students come up with their own lists of singular and plural nouns if they are able to. Read the story back to them with their answers filled in and talk about what parts do and don’t make sense. Have fun and remember that in this case the sillier the story is the better!