I’m not talking about making bird feeders are crap like that I’m talking about making some awesome one off items. It’s like a poor mans 3D printer but more hands on. Anything that is made from HDPE or PEHD with the recycle number 2 on it can be melted and used in molds and cut with simple wood working hand tools. The plastic is very dense when you have turned it into sheets or blocks. Also you can get some “groovy” looking patterns out of it when you mix different color plastics together.
It’s very simple. You can use a toaster oven, sandwich grill or what have you to heat the plastic up to 350*F (177*C). Just cut up the plastic into small pieces or if the misses isn’t looking you can use a blender. Heat up the plastic and be sure to be in a ventilated area and wear gloves when handling the molted plastic. Press it into a mold and clamp it for a couple of hours. Do not force cool it because it will shrink like crazy.
There are guides all over the net on how to achieve on making stuff from HDPE.