Garden plans 1

north is down

So let me try to list what I want to do with the garden...
First and maybe easiest is the backyard patio. It is paved with red stepstones, and is 3 tiles wide. The problem is that grass keeps growing out from between the tiles, plus there is a 1/2 tile wide narrow gap between the house and the paved part, where real thick grass has grown. Kind of ugly and high maintenance. Also, there are 3 long holes in the paved patio where tiles have been left out intentionally in order to plant flowers or what not. But the holes are badly positioned and I just keep stepping into them when I walk there.
My solution, or at least my plan, is to bring the patio closer to the house, and get rid of the gap. I have to check and make sure that by doing so I don't accidentally cover some breathing hole underneath the building. Also I want to make the patio wider (4 tiles wide), and also cover all the long holes. Also, I need to fill in between the stepstones with something more than just dirt to prevent grass from coming out so easily.

... you get the idea ...

Not sure though if I should put the tiles directly on the dirt or if I should make a concrete base first. It is not only about preventing grass from coming out but I have to think about drainage and such too... maybe a sheet?
Anyway, I hope my actual results will be less shitty than my attempt to draw the design...
Here are a couple of before pictures. As can be seen, I already had begun filling the long holes with tiles before I realized I should do it properly.

only 1 tile left to the right before all long holes are covered

To make 4 rows instead of 3, I will use the tiles from the divider

The divider seen in the above picture fills no purpose and I'd rather plant something there instead.