Crossword Labs is a quick way to put a crossword online. PuzzleCraft is another free option, and it also prints a full answer key without a passcode or membership.
Start with your own words and clues, bulk-paste a whole vocabulary list, or type a topic and let PuzzleCraft suggest words and clues for you to review. Students can solve on a screen with a share link, or you can print copies for the class.
PuzzleCraft also makes word searches, and it has daily puzzles and a Kids Zone with math games and printable worksheets.