I would suggest just using a box until you decide if you like making soap and what kind/size you want. Then either make your own molds (very easy to do) or buy them. Use freezer paper, shiny side out. What you need to do is once you find a box measure the inside, w x l x height you want. Multiply that x.04 to get the amount of OILS that you will need (not oils and lye together). Then run that thru a lye calculator so you will know how much lye and water to use. Have you read the miller site yet? I read and researched for about 6 months before making my first CP