Baby not crawling yet but wanting to stand

Help! My little one does do tummy time but spends more time sat, and trying to reach for toys/move forward from sitting and can’t quite figure out how to move his legs to move into a crawl position. He has also taken to wanting to stand up, he can bear his weight on his legs for a good 20 seconds (albeit wobbly). But I’m so conscious he’s not crawling so wanted som tips please!