Window clings are a great way to keep children entertained for hours on end, especially young children who have a limited supply of soft and safe toys available to them(as long as you make the clings big enough that they aren't a choking hazard). They also make fun holiday decorations that can handle the use and abuse of little hands.
They also make great gifts for kids of all ages; I made a bunch of nativity clings for my nieces and nephews for Christmas this year and not only were they inexpensive to make, but the kids loved them too.
When I first got interested in making my own window clings I found a ton of variations of the glue and dish soap recipe; all of which worked OK for a day or so but eventually dried out and were much too fragile for a little kid to play with. They were so cute and vibrantly colored, but even the best of them was ruined pretty quickly because they are so easy to rip and they lose their adhesion so fast.
After a few failures I finally came up with something that will stay sticky and is much stronger than even some store bought window clings.

Step 1: Materials

You don't need a whole lot for this project and it's all pretty inexpensive.
You will need:
Clear silicone
Dish soap (any liquid soap will work)
Large bowl
Rolling pin
Aluminum foil (or something else to cover you work surface such as wax paper)
Food coloring (liquid or paste is fine)

If you've seen those tutorials on moulds form silicone and dish soap, it's pretty much just that with a slight alteration.

Step 2: Roll It Out

First fill your large bowl with water and add some soap, about a tablespoon per gallon of water. Make sure it's mixed well but not bubbly.
Add the silicone to the water/soap, how much you add depends on how many clings you want and how big they will be. It will vary based on how thin you roll it out, but half of a silicone tube ends up being about 12 in by 18 in if you roll it thin enough.
Use your hands to knead the silicone into a ball (make sure they are soapy first or it will stick to you), keep it in the water as much as possible to keep it from getting too sticky. When it's in a nice ball set it on your working surface (again, make sure it's soapy. To do this I just scoop a little water from the bowl and smear it around). Use your palm to make a depression in the middle and add some food coloring. If you want it really vibrant then you will have to add quite a bit because the dish soap kind of dilutes it.
Carefully knead the color in; this part is a little awkward since the coloring has a tendency to drip off at first, but keep at it and you'll get it eventually. Note: I find it easiest to knead mostly in your hands rather than on the table, but do what works for you.
Once it's the color you want begin rolling it out on your prepared surface with a rolling pin that has been dipped in soapy water. Be sure to start with it in the center of the surface so it doesn't squish over the edge, unlike dough this is not easy to pick up and reposition. Roll it out to the thickness you want, keeping in mind that the thinner it gets the paler the color will be but the thicker it is the heavier it will be. I had a rough time trying to keep it round but it's still usable even with a funny shape.

Step 3: Make Some Shapes

If you want you can try cutting out shapes with cookie cutters while it's still wet, but since I didn't have any I didn't and therefor can't tell you
how well it works. If you do try it please let me know how it went in the comments below. What I did instead was wait for it to dry (it takes about 45 min) and then cut it out by hand. This requires some patience and creativity, but then you are only limited by your imagination rather than what shapes you have on hand. I googled nativity silhouettes for inspiration. The sky is the limit really.
I noticed that when cutting curves it was hard to make them smooth unless I did it all in one cut. I also had to simplify some of my designs since cutting through something that thick is tricky.
To be sure my shapes worked out like I wanted I drew them on paper and then set the silicone on top and traced it. You could draw right on the silicone but it's kind of hard to get it to look right when you do it freehand. This is also a good way to make them uniform of you want to make several of the same shape.
If you are having a hard time cutting a certain shape then try bending or folding the silicone, just get creative and you may be surprised at how it turns out.

Step 4: Use and Care

Once it's all dry and cut out I recommend rinsing your window clings before using them because they have a bit of a residue on them. Then you can use them like any store bought clings; they stick to any flat surface and won't dry out. I have noticed that they eventually fade a little bit in the sun, but this can be compensated for by adding more color to begin with.
If they get dirty or lose their stickiness just rinse them off (use a little soap if they are really dirty) and go back to using them like before.
I have found these to be great for car windows on long drives, bath toys, quiet toys for church (either bring a board or stick them to the bench in front of you), and since they stick to anything flat they work on stainless steel refrigerators when alphabet magnets won't.
My daughter loves these and I hope you like them too. Thanks for reading!