OK
I know something about this.
Basically you need 2 blocks of slate which have to be matched up face to face so that they are level and even, you then need keys at each end of the block to hold them together tightly, normally but not the traditional way is the let into one block copper rods and have holes in the other blocks so they mate together, using the male & femaie technique. The the two faces' once matched have pencil marks on them to establish the center of each block ,usually you have a vertical and horizontal line as you need to find the exact center. You can also have more that two lines you can have a star shaped grid to help establish the position of arms legs etc. These measurements need to be established on both blocks and must match exactly, any deviation however slight will spoil your moulid
Your design should show back and front design, I have attached an example and they should be placed on paper in such a way that they can be folded back ontyo each other to ensure that they match precisely..
You then transfer your drawing to the two pieces of slate one has the front the other the back, engrave YOUR FIGURES CHECKING Constantly through the use of modelling compound, beeswax, plasticine etc, to check both the depth of the engraving and the positioning, once done you have to cut moulding lines from the figure to the edge of the mould, this is to allow air and hot gases to escape when you pour your metal and also the encourage the hot metal to flow, So moulding lines from hand, legs cloak etc.
Airfix used to sell vulcanized moulds in Germany and if you can get one of those it will help you with your pouring lines etc. Hopes this helps
