There's so many boring paving slabs out there and I thought I'd have a go making my own for my allotment.

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:

Cement
Sand (I used soft as opposed to sharp sand)
A leaf
Water
Bucket
Trowel
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

You'll need a fairly big leaf. I'd avoid leaves such as giant hogweed as the juice will burn you if you're in the sun.

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

Concrete can be made in so many different ways - it's very similar to making a cake. I've absolutely no experience at mixing concrete. Here are some safety considerations:

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

At this step, it's fairly self explanatory, you're just smothering the leaf with concrete. Depending on the use, you may need to make this quite thick (about 3-4") and for extra rigidity add chicken wire reinforcement (will need to be cut to same size as the leaf). The concreted leaf here is about 2" thick.

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

The concrete takes time to set. Due to the weather, I needed to move my leaf inside overnight, but it was set by the morning. It hadn't bonded to the wood so a gentle nudge and it came straight off.

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 deep veins should stand out very well. You can paint it, however I quite like the concrete look. There are clear sealants which you can apply for outdoor use which soak into the concrete and give it a better bonded surface. The advantage of all these veins is also more grip, useful on a garden path in the rain!

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!)