The master shape for a miniature bottle can be made from all kinds of basic shapes. I chose to use a large ended embossing tool as it had the round shoulders I wanted for a miniature bottle, as well as a fairly thick metal end which could serve as a bottle neck. If you wish, you can modify a base shape by adding two part epoxy putty, and sculpting the correct bottle shoulders on a cylindrical bead, or use a bit of epoxy putty to modify the neck of your bottle or to change the shape of your bottle shoulder, . (This may not work, depending on the type of casting material you use, see later steps for more info).
Measure out how long you want your bottle body and use a marking pen or a piece of tape to mark the bottle base position on your master. (see photo). Also mark how long you want your bottle neck to be if possible (air bubble gremlins make think otherwise!)
The final preparation is to make a stable support for your master shape to hold it until the mold putty sets firmly. The easiest way to do this is to fill your mold container with enough modelling clay to hold your master shape firmly at the top end, while making sure the bottom end is at the top level of the container (check the marks you made with markers or tape). I made a second, simpler bottle shape from a rounded pen tip holding the pen refill out as far as possible in the pen housing with a piece of masking tape on the base end away from the tip. The flagon based bottle in the tutorial introduction photo is made using a fairly ornate platic bottle cap as a master.
