ALTAR PENTACLE
Buy a wooden disk at a craft store and paint it black (or use a magic marker); then with a gold-paint marker, draw a pentacle on the disk; add other symbols if you wish.
HANGING PENTAGRAM
Find a bunch of small, fallen, tree branches and form them into a pentacle shape. Then use some brown thread and tie the branches together at different spots.
PENTACLE VESSEL/BOTTLE Buy some black sculpey clay (if you can't find that, acquire fimo, or another soft, modeling clay substance). Roll the clay into a ball about the size of a shot-glass. Make a hole in it with your fingers so that it starts to resemble a tall bowl, pinching inward the open sides so that your ring finger fits in the hole. It should look something like a bottle with no neck (a cork will go into the hole); then, with some more clay, (a tiny amount), roll it into a "snake" like one does with play-dough as a child. Make a small, thin pentagram (five-pointed star) on the bottle and enclose the star within a circle (in other words, make a pentacle). Make it perfectly; if you mess up, peel off the pentagram and try again. Bake it in the oven at 275 degrees F for about 12 minutes. Watch it so that it doesn't burn. Stick a small cork in the opening when it's done. Then, you have a magickal bottle for salt, herbs, potions, or anything magickal.