Let's make a cauldron. Cauldrons are great for bringing potions because they can hold water to fill up your bottles with. Just put iron ingots in a U shape here, nice and easy to remember and you've got your cauldron. So, you can go and place this down and to fill it, you need a water bucket and just right click and fill it up. Then you can take up to three water bottles and fill it up and you'll see it holds enough water for three bottles.