Hi @dsl400 
I believe it should be possible to serve DocSpace from a subpage like my-site.com/docspace.
While I haven’t personally tested this setup, there are no specific instructions for DocSpace, unfortunately.
You will most likely need to configure proxying on your reverse proxy server.
I recommend taking a look at the following examples that deal with proxying for ONLYOFFICE Docs. These should give you a good starting point: