Please see the conversation at the below url, you should not have to create a connection in flow before you can use the create blob connector, it should be dynamic - you should be able to pass the storage account and key along with the file path, file name and blob. I have 110 users, each need to store their files in their own storage acocunt and right now i have no way of doing this - with the exeption of one way which seems like a back door to application problems.
That one way is when a user logs in to the PowerApp, they are prompted to agree to, connect and/or sign in to the various connectors. While this seems like a good idea, we should be able to lock this down and force the user to use the connections that came with the app - otherwise they can change the storage acocunt to something esle. Much like 'Execute As' in SQL Server, the user should have permissions to use the connectors/credentials that were used when the app was created as long as they are used in the context of the app and creating user (or specified user credentials).