finishing ash table with marquetry motif

Hi
i have just completed a demi lune table in ash. I have added a small floral marquetry motif made from sycamore and walnut veneers.
I have decided on a combination of light oak dye followed by a mahogany gel pigment stain and clear urethane varnish top coat. i have tried this on scrap ash and really like the contrast. I want to leave the motif as it is though. What is the best way to prevent dye and stain getting on the veneers. It is a simple oval shape and it wouldn’t be too difficult to cover up with masking tape. I wondered about other methods that might be recommended, particularly if the motif was a more complex shape?. Will post when completed.

cheers

jonathan