Summarize:

Soap molds are basically boxes for the liquid batter to set in. Any dry plastic container works, or you can buy silicone molds specifically for soap. If you have a wooden container, cover the inside with a silicone liner or freezer paper. Soap molds are available online and at some general stores. If you need a liner, freezer papers are available at most supermarkets. Fill each mold close to the top. Tap the mold against a hard surface a few times to break up air bubbles. Use a rubber spatula to scrape out excess batter to pour into a different mold or throw away. Bump the mold against a hard surface a few times if it looks frothy. Try dropping it from a low height to knock out stubborn air bubbles. Don't worry about breaking the soap into smaller bars yet. Wait until the soap solidifies for that. Tape a piece of cardboard over the mold to cover the soap. Then, wrap a towel around the entire mold to insulate it. Doing this helps the mold set properly, leading to better soap. If you don't have cardboard, place parchment paper over the mold. The saponification process takes at least a day to happen. When you remove the soap from the mold, it will be hard and ready for cutting. Use a sharp kitchen knife to break the soap down into smaller bars. To smooth out the sides, scrape the soap with a vegetable peelers. Keep your soap at room temperature and out of the reach of children and pets. If you used fresh lye, the soap is still dangerous to touch at this point. If your soap is too soft to cut, let it rest for an extra day. This happens most often in large, single molds. Move the soap bars into a cool but well-ventilated area. Try placing them near a window in your basement or on a countertop. Put them on top of wax paper or another disposable material to prevent the oils from damaging the surface the soap is on. Soap takes about 4 weeks to finish curing. Soap can take anywhere from 3 to 8 weeks to cure completely. The time it needs depends on the oils you used. Check your recipe for the recommended curing time. Soap made using the melt and pour method typically solidifies within a few hours. At most, let it rest overnight before taking it out of the mold.
Clean and line your soap molds. Pour the soap batter into the mold. Wrap the mold inside cardboard and a clean towel. Wait 24 hours before cutting into bars. Dry the soap for several weeks before using it.