[mrs bouquet]

A few years ago I rescued from a Garden Centre a granite base of a water feature.  (free)   Somebody drilled me 4 tiny holes in it about pencil size.  I filled it with a mix of sand and soil with some crock in the bottom.
I have notice that it has become a new water feature.  The plants have had it and it is covered in moss.  Today I have dug out the soaked soil and gravel and managed to bin it, then lifted the granite base onto its side.  It is 20 inches square x 8 inches tall and the granite is 1 inch thick.    I have been advised to buy a diamond drill bit, ad make the existing holes bigger, and carefully drill a couple on one side which has no holes.
When I have done this, what do you advise refilling it with (I have bought some saxifrage and pritzalago and mini-pinks to go back in and shall shall add some of y house leaks.)
I am anxious to get the soil mix right now.  I have got some horti grit, but can get perlite or vermiculite as necessary.     Any advice please.    Thanks,   Mrs Bouquet

[snowdrops]

I’d think the grit mixed 50/50 with compost would be suitable with a top dressing of attractive gravel/grit on top to set off the new planting

[mrs bouquet]

I am thinking of lining the base with some matting so that the holes don't get bunged up.  Mrs B

[Goosegirl]

I think that would bung them up so why not get the grit into the holes then put the soil on top of that so it will drain better.

[snowdrops]

I don’t think you need any matting Mrs B, just lots of crocks, then the soil & grit mixed well. Remember most alpines grow in crevices & cracks with very little actual soil, the grittier the better

[mrs bouquet]

The drill bit is due later today, so I am going to start preparing the mix.  I shall probably have to smash  pots to get enough crocks for the bottom. Better search for my safety goggles as well.   Mrs B
Thanks for your replies.