Broadback wrote:
It seems to me that slabs are rather expensive, so I am thinking of
making some. I need the slabs to have a bar texture on top so that they
are non slip when laid on a slope. Anyone any experience of making
these, also a source of moulds please?

What I've done - not exactly for this.
Obtain a large 2" sheet of polystyrene.
For 50cm slab.
Cut 3 80*80cm squares.
Cut out 50cm square, with side relief. | \ / | (so it comes
out easily).
Stick this to the bottom slab with contact adhesive or something.
To use.
Spray with vegetable oil.
Weigh out quantities of small aggregate, sand, cement, water, and mix in
a bucket, using a drill mixer, and boiling water, with some accellerant.
Pour into mould.
Place some string loops into the mould, so that you can lift it out
easily.
Place top on mould.
Cure, repeat.
Edit the mould using a sander on a dremel, or a blowtorch.

Alternatively, you can use a greased concrete mould, if you saturate it
with grease, and the relief angles are adequate.
Having a valve or hole, to introduce compressed air or a hosepipe into
the back, to press it out, may make it easier.