Soft connection, if you are looking for cleanliness. Black pipe says old fashioned
Sorry - I am a plumbing SNOB. I use stainless braided teflon core hose with a female SAE45 flare '08' ends (Series P/N) directly to the flare to pipe orifice fitting. Brass nipple, nut and shell unless I feel like stainless, which looks much better. No fitting stack, and no black iron pipe. This works for stands that remain plumbed all the time, or, like my BK, I use brass QD's and can transport the propane tanks and even hide them away in storage. I also have a needle valve option for the flow control.
My company does make a lot of pipe to SAE45 options, if you need more help. I can get you some to help out, but it may take two. Black pipe does not give you the option of anything but pipe threads. You could flare copper tubing as one of the previous posters did. Copper is easy to work with, bending and flaring. Nuts are available in many lengths for tube support applications.