To make a garden gnome, sculpt a model from clay and place it at the centre of a plastic board. Cut a piece of PVC and roll it into a pipe, then spray the inside part of the pipe and the model with cooking oil and place it on top of the model. Seal the bottom of the pipe using a roll of clay to join the pipe and the board. Mix liquid silicon and put the mixture inside the pipe. After the mould has cured, remove the clay at the bottom of the pipe and remove the pipe from the mould. Divide the mould into two and get the original model from the centre.