I knit some flat worked fingerless gloves, so I have to seam them.

Well I’ve looked up videos on how to seam, and I understand that part, but I can’t find any videos telling me how to close it off and make a thumb hold or how to end it period

Can someone offer some advice or point me in the direction of a good video on how to leave a thumb hole and what to do after you get it stitched up?