lol they did, after many iterations of trying though. They made improvements on the design over time. Khufu's Giza pyramids were the best ones but were also the last to be created after the Bent and Red pyramids among others.

Slaves were most likely used as the Egyptians had plenty of them, slave being a loose term because they were paid in bread and beers and had certain rights and freedoms. I mean, at one stage they even had the Jews who had to work until Moses became Mandela of the Jews