This is hands down, the cheapest way to make molds, it's fast and you could re use the molds several times.
If you don't need perfection, your item has simple shapes or want something quick you can use this method.
The mold will be slightly flexible, just enough to make the duplicate come out easy. But rigid enough to hold the shape without needing another harder layer. It holds a fair amount of detail, just look at the size of my pony (less than 1 inch)
Are you ready? Grab your always usefull hot glue gun and let's get started.
Step 1: Gather Your Materials
A silicone mat or parchment paper
Hot glue gun and glue sticks.
Oil (I had coconut but any kind of cooking oil will work)
The item you want to duplicate. Just be sure it won't be damaged with the heat of the glue. I've used this method with several plastic toys and they've come out really nice, except for a vintage Polly pocket doll that her painted face disappeared with the glue, but that didn't bothered me.
Step 2: Make the First Half
First with your finger coat the item with oil, make sure you cover it entirely with a thin layer or it will loose detail.
Now wait until the glue gun is very hot. In your silicone mat make a circle with the glue. To make it easier and bubble free, don't move the gun, and make it as big as your item and as thick as you can.
Place immediately your item in the centre of the glue, push it slightly, make sure the glue covers all the sides of your item. Wait until the glue is completely cold (it should look like frosted) to peel it off the mat.
Don't take out your item until you have done both parts of the mold.
Step 3: Make the Second Half
Coat again your item with oil, this time you should pay special attention to the glue, coat your item with a thin layer. But in the glue the layer of oil should be thicker.
Now place it on the silicone mat. Start pouring hot glue at the highest part of your item. Don't move the gun to avoid bubbles. The gravity will make the glue fill all the little spaces and go all the way down to the mat.
Wait 3 minutes, if you see that the highest part has a very thin layer of hot glue, you can add more in that spot. Your item will look encapsulated. Again wait until it's completely cold. When you are sure it's cold, let it cool another 15 minutes. Because the centre of the mold could still be warm.
Step 4: Open
To open it up, just pull both sides of the mold, you can use a sharpless knife as a lever.
Ready to be used! You can fill it with any moldable material, as long as it's not hot it will work. I used polymer clay. Fill both sides, then press it firmly and carefully take out the duplicate. Finally cut the excess with a craft knife.