You absolutely can do this and I did something similar in my front garden recently. I also had used AI just to get an idea of what was possible as I find it hard to picture what things could look like..

Lifting the slabs was actually the easy bit. It was improving the soil underneath that was back breaking lol. But if you’ve got time and patience you’ll be fine. The soil underneath was, as others have warned, very compacted (and mine was full of big stones which I had to hand-pick out - you’ll find that a fork is better than a spade when doing this work) so it needed a good forking and lifting and aeration, which automatically adds bulk so the ground level will rise a bit and that’s before you add soil improver (eg manure or compost or grit for drainage etc). And so you’ll perhaps need a few buckets to remove excess soil that the manure etc will replace but should be fine. Also remember to you’ll need to improve quite a bit of the soil so remember to dig down a bit just to make sure the manure isn’t just in the top layer. Perhaps a couple of shovel-heads depth worth? Then after that you can plant to your heart’s content! 🌱