You can't craft in your Inn room, but you can craft in any other sanctuary. While there, you get a slow exp boost, so hop a choco, teleport, or drop by the nearest sanctuary outside town for a nice little exp boost to crafting.

Taking just under a minute per synth and crafting recipes a few levels below me around level 30, I saw a boost in the neighborhood of a food bonus. Not worth doing for just a few synths, but if you are going to spend an hour or more crafting it's well worth it to grab your materials and get to a nice spot.