Okay, I see what you are saying now about the 404 error: I didn't comprehend what you were talking about when you referenced the 404 the first time (my root www.joekalb.com was returning a 404).
That fixed it! I now have it set up with NakedSSL (it will take some time for the DNS to propagate everywhere; I will plan to follow up after a few days to confirm whether the NakedSSL works for the subdirectory once the DNS entries have had time to propagate).
Thank you for your help, Glenn.
For reference, for anyone else:
My web app (www.<mydomain.com>) was returning a 404 for the root level (e.g. www.joekalb.com returned a 404), while I had working subdirectories (e.g. www.<mydomain.com>/<mysubdirectory> AKA www.joekalb/swflholistic returned HTTP status 200 and a real Web page).
Because my root page (www.joekalb.com) was returning the 404, NakedSSL.com was giving me an error message that said "We can't redirect your domain. Check your URL again and ensure you have a SSL certificate installed. These guides get you started:". This got me down the path thinking I needed an SSL cert when in reality, I just needed to be returning a valid 200 status from my root http://www.joekalb.com
After returning a boilerplate 200 status and "Under Construction" text at my root domain page (www.joekalb.com), NakedSSL recognized that it can successfully do the "naked-to-www" forward. After doing the basic setup outlined in the NakedSSL setup process, requests to https://<mydomain.com> are now getting successfully forwarded to https://www.<mydomain.com>
Thank you for your help, Glenn and team. Again, I'll plan to confirm in a few days whether the NakedSSL solution works for the subdirectory (e.g. confirm that https://joekalb.com/swflholistic does indeed forward successfully to https://www.joekalb.com/swflholistic)