Depending on what welding experience and equipment you have, it should be pretty straight forward. My first choice would be gas shielded flux core MIG welding. In my experience, the flux cored wire is usually shielded with straight CO2. Probably use a bit longer stickout than what you're used to with regular hard wire mild steel mig welding. Use a push welding technique rather than a pulling method. Most likely you'll have to run it flat, no out of position welding. 045 or larger flux core should be available through a weld supply outlet. Do some test runs before moving to your actual joints to see how it runs.

Depending on the filet depth called out or needed for your joint, stick welding with 3/32 or 1/8" rod would be the next logical choice. Running the root with the smaller rod then capping with the larger rod would be my suggestion.
Stainless is going to draw like a bugger so you will see those baseplates curl up toward your weld. The bigger the fillet, the bigger the curl. I'm not sure you'll need the bevel in this case, sounds like a basic filet weld and you may have less chance of slag entrapment without the bevel.