Hi
I will just tell you that the material you desire is in the naphtha layer after the repeated shakings and does not really depend upon the container that the mixture is in.
However roast/oven dishes are shallow and have a large surface area. So maybe don't use a deep and narrow jar. Ideally a lot of crystals precipitate out and you will catch them in the coffee filter anyway. With the rest clinging to the surface of whatever vessel you choose, to be scrapped off.
Remember to use precautions when working with caustic soda such as gloves and eye protection.
Hope that helps and be safe.