After all clay characters are complete
photograph them on each of the background colors.
Open each image in photoshop and follow the steps to remove background (step by step is listed here Photoshop Instruction - Removing Background )
Determine which background color is easiest to remove for your characters
Post the Ideal background image into the community here
After photographing the movements of your animation
Load all images in one Photoshop doc. (See Photoshop instructions - Load Stack)
CTRL+T on each layer to resize images
Line up each frame to see progression
Add the background you will be using
Post to community