A work sample is any paper, video, photo, or other item that your child produces that records evidence of their progress. Keep a few of these to show your child’s progress in each academic subject that you teach each year.
Almost all children will create something that you can save, but if your child has special needs and functions at a level that does not allow them to do this, then the work sample requirement does not apply to you. Instead, several dated journal entries each year describing their activities and progress will work just fine. Use your judgment as you do with everything in your homeschool and do your best to keep records that can show that you are educating your child as is developmentally appropriate.