My son didnt crawl until 14 months onwards - but he is late to crawling due to his conditions affecting his movement. You could try a ball that's made to encourage crawling, I found it in B&M for £6 and my son likes chasing it. You could also go behind your baby and move their arms and legs to get a feel of moving them to crawl - suggested by my son's physiotherapist x
I put baby in different tummy time exercises. I did row row row your boat on an exercise ball, and I put her tummy down on the floor or bed and then start dancing around her. Or I go to the local playground and plop her tummy down watching the other kiddos. I feel like with enough strength, she just figured out the most efficient / fastest way to crawl
My girl was army crawling since 6 months old, started rocking back and forth at 7 months, crawled „properly” a few steps the day she turned 8 months and then for 2 of 3 weeks was going between army crawling and normal crawling until she realised she was faster proper crawling. Honestly I don’t think you can do much, they will just figure it out on their own ☺️