Help newbie with lid camera, Jiggy Jigs... Snapmarks etc

@marmak3261 thank you so very much for sharing your jig for the pencils that really made things even clearer for me. I see your cardboard / jig set up seems to fill the floor of the GF, is it best to remove the crumb tray?

In the video referenced above in @dklgood post they use what I believe to be magnets to hold the jig in place… are there specific magnets that are best? I did print out some of these pins - do you have a preference?