This particular slab is actually for aesthetics only, You can making this for stepping on, you just need to apply a couple of inches more thickness than I did and add a bit of chicken wire.
You will need:
Sand (I used soft as opposed to sharp sand)
Suitable flat surface - thick cardboard if you're not going to move it, I used the top of an old desk.
Knife for opening bags if you need it
Gloves/other general safety gear as appropriate.
Screwdriver or similar sharp pointy implement for getting in crooks and crannies.
Minions - This time I needed a couple of minions/friends/assistants about to take photos and assist with general jobs. You'll probably need a hand when doing this.
As usual having researched the project and not finding anything like it on instructables, the robot links it directly to someone who's done exactly this, but with some neat ideas. You can see it here
Step 1: Picking a Leaf
I used a rhubarb leaf as it's in abundance at this time of year, but you could use all sorts.
I'd use a large enough leaf you could step on.
*no minions were injured in the leaf picking process
Step 2: Concrete
1.) open the cement bag in a plastic bag. This stops it going everywhere
2.) If not opening in the outdoors, wear a mask.
3.) Use gloves when mixing and applying concrete
I used a 50:50 mix of eight cups of cement to eight cups of sand. It seemed to work well with about a litre of water. I didn't add the water slowly but all in one go, assuming I'd need more, but I didn't and had to add more cement and sand (so it's not a disaster, just add equal amounts)
When it becomes a thick paste, you can apply to the leaf
Step 3: Covering the Leaf
Concrete needs to applied upto the edges - you don't need to go over the edges however. The stem doesn't need to be covered either - as you can see in the later pictures, the stem is still exposed.
*The excess stem of rhubarb makes excellent crumble and feeds your minions.
Step 4: "leave" Overnight
Now comes the slightly tedious bit - peeling off the leaf. There's no hard and fast rule on how you take it off, just peel it bit by bit. Be sure to properly support the leaf whilst you're doing this. The last thing you need it to do is break! The weakest point will be where the veins are.
Step 5: Fin
The slightly brown areas are where rhubarb leaf juice got on it and stained it. I think this looks quite pretty and more natural. This is why sealing them can be a good idea!
If you want to lay paving slabs, dig a hole same shape as leaf and line with sharp sand, bed down the slab by tapping it with a wooden mallet (gently!)