Non slip socks

i just finished a pair of socks for my husband, and he is scared to wear them and slipping and falling. I have googled on how to remedy this, but am wondering what you do.
I am also interested in any way to knit them nonskid as I go along.
This is the first time he has worn hand knit socks, and he loves the way they feel. Fraternal, but they fit 😊