Cut paper (I used coffee filters) into strips about 1/2" wide and a 2-3" long.
Submerge the strips in cabbage juice until they are fully soaked.
Remove the strips and place them in a warm spot to dry.
Store the dried strips in a resealable bag.
To use, place a drop of the liquid to be tested on the paper. If it's a base, it will turn pink. If it's a base, it will turn green. And if it's neutral, there will be no color change.
The color change isn't as drastic as you'd see with litmus paper, but it's there.