Freezing the background in a gif allows you to use more frames than before, because with not all parts of the gif moving, the size of the gif reduces.
1. Open the frames for the gif you want to use and set the speed. Add some colorings if you want too; basically, make it look like you want the final result to be.
Then select the last layer, right click and Duplicate Layer.
2. Now drag your duplicated layer to the top of all the other layers, and then click this symbol to Add a Layer Mask.
And now this white box should be on your duplicated layer. It’s important to make sure that the duplicated layer are visible on all frames (the eye).
3. Now go select a brush, I usually use a round, soft brush, around 65px. The colour has to be black. Now click that white box and start painting on the part of the gif you want moving. In my case, I want Katherine moving so I will be painting over her.
Now the box will look like the picture above. Keep using the brush until it looks more like this:
4. Play your gif to make sure everything works as it should. If not, then keep painting over the moving parts. Then go save your gif. Here’s my result:
Without freezing the background, it would have looked like this:
If you’ve got any questions, just send me a message!