This is my first tutorial, so do not blame me. I will tell you about the creation of a mold from silicone sealant and starch, and then, on its base, I will make a cast of acrylic sealant.
The application of this technique can be seen in the example of my work — the "Blue Wonder" box with a lid.

I have been interested in this topic for a long time. I've also experimented. First there were my first bad experiences, then I did better. And here, in this tutorial, I decided to share with you my own experience of creating a mold out of silicone and starch, as well as creating on their basis single-piece sheets and individual volume elements of acrylic sealant with the filling of Pebeo fantasy paints. I used a mat for stamping on clay. I tried to take pictures of the whole process in detail, as they say, a picture is worth a thousand words. I thought that my experiences could be useful to someone and would help to avoid unnecessary mistakes, I would be very happy. Enough talking, let's start!

So, for the work we need the following materials:

• Silicone sealant.
• Acrylic sealant.
• A gun for extruding sealant from a tube.
• A disposable bowl and gloves.
• Regular food starch.
• A rubber mat for stamping on clay.
• A spatula.
• Aerosol spray paint.
• Pebeo paints: fantasy prisma, fantasy moon, vitral, ceramic.
• Pebeo contour (contour paint).
• A clear pocket, a rolling pin.
• Scissors.

Insert the tube of silicone sealant into the gun for extrusion, be sure to wear gloves, squeeze in a bowl.

And gradually, little by little adding starch, mix the mass.

It sticks to gloves, it is not very nice to knead it, but you must be patient. It's for you to decide when to stop adding starch, the mass mustn't be thick, so it is possible to put it on a mat, it also mustn't be very tough.

Apply the resulting silicone to a stamp (a mat) for stamping on clay, like this one:

Mash it, pressing well.
Cover it with a clear pocket or a package and roll out with a rolling pin.

Remove the clear pocket and let it dry well for a couple of days.

Turn out and remove your own finished mold.

The mold is quite flexible.
The pattern was convex on the mat, it is sigillate on the mold.

Insert a tube of acrylic sealant in the gun for extruding, extrude it on the mold and make it even with a palette knife.

Dry, remove the resulting cast, an exact copy of the original rubber mat with a raised pattern.

Trim the edges of the cast with scissors.

Thin cast of acrylic sealant is very flexible, you can bend it as you like, even roll it.

Paint the resulting cast with an aerosol paint, I had silver paint, but you can use any paint, gold paint, for example. Let it dry.

Then, depending on the purpose of the use, cut the painted cast into pieces or leave it like it is.
Take Pebeo paints: prisma fantasy, fantasy moon, vitral, ceramic, mix them well with wooden skewers, especially fantasy prisma and fantasy moon, for each paint you must have a separate jar. Drip some paint in the resulting cells, selecting colors and creating your own unique picture.

Since we use Pebeo fantasy prisma, dry all together for 72 hours. If the cast of acrylic sealer is cut into pieces, go through the edges with a finger with Pebeo contour.
Glue the finished cast to a work and admire the result.
Hope everything is clear written and my experiments will be useful to someone. If there are doubts or questions, ask, I will answer them with pleasure.