In-patio bed - Houston - did we think this through?

[Tetrarch]

In a rush of ambition-over-practicality we saw, what we thought, looked like a really great idea to break up a large area of patio (see pics) with some grasses etc

What I have now is a space in the patio (see pic) and no certain way to protect it after planting. My plan is to dig out a narrow 6" deep trench, pop in some shallow concrete gravel boards and then dig out the interior.

Any thoughts/criticisms/alternatives?

Regards

Tet

 

[Why Not Indeed]

What is the now-exposed bed in pic 1 made of? Can you dig it out without disturbing the tiles? It's going to look like **** if they end up uneven and cracked!

 

[Tetrarch]

The exposed is compacted MOT. It's replacing an existing patio that had been there forever so should be fairly stable underneath. The idea is to dig out whatever MOT is needed without compromising the integrity of the new pavers

Regards

Tet