When you find the ooze, you'll probably quickly discover his mechanic involves destroying all the eyes, which gives you a limited window to than shoot his heart. If you shoot his hear before killing the eyes, it does 0 damage.

I found, the easiest way to kill him at the moment is to first build little tunnel under his room. This lets you kill the eyes fairly easily by just knocking a hole in the cieling and shooting up. Close the hole and move to the next eye.

Kill all the eyes but the last eye. There is no rush during this process. If you are low on health, teleport out and heal up and return.

Once you have one eye left, start filling in the space where the eyes spawned. If you kill the last eye, the eyes will quickly return and you'll have to deal with this fight all over again. So its important to leave that last eye while you do this.

Just fill in the spaces where the eyes previously where. Once you've done that, go into the center and stand next to the heart. You should behind the last eye at the point, so kill the last eye and fill in the space with blocks.

Now, the eyes will respand, but you should be safe. Look at my picture if you need further help. You can safely shoot the back of the eyes and no beams will hit you. You are right next to the heart and can quickly kill the boss.