It's fairly easy, but really messy.

TOOLS:
1 - Make sure you have a dustmask that specifies it is rated for stone. Those cheap ones won't do.
2 - Goggles for eye protection.
3 - angle grinder and diamond blade
4 - 2 clamps and a strip of wood longer than the blocks
5 - heavy mallet or hammer

METHOD:
1 - Clamp the wood strip near where you want the cut, far enough away that you can slide part of the grinder body along it and get a straight line.

2 - make several passes along the cut line until it's scored 1/2 inch or so deep.

4 - Turn the slab over, propping it up on something so the part you are cutting off is unsupported.

5 - Whack along the cut line with the mallet.

They usually snap quite cleanly along the cut line. If it doesn't, turn it over and deepen the cut.

Many sandstones are very easy to cut with no more than a good hammer & chisel.
The snapped edge is far more appealing without the sawn line at the surface, IMO.

What type of stone will you be buying?

It is a yellowish colored stone sold at a local nursery at a rate of 18 cents a pound. It is already cut into foot long blocks. I read elsewhere on the forum that sandstone splits if it gets wet and freezes. Is this so? It does freeze here in Zone 7a and I was hoping the stone edging would last.