I usually stand mine in a flower pot tray, either plastic or terracotta, that's the right size. That keeps the soil in the pot, but of course, it's not easy to move the pot after its planted. You do have to watch your watering though - the water ends up sitting in the tray, but it isn't usually much of a problem in summer, and if the tray fits closely, it doesn't hold much anyway.

Pond liner?
A good fitting plant pot at the bottom could be used to hold gravel to help with drainage, instead of the bricks if you want the extra depth of compost.

Before you fill them make sure to scratch your house number and postcode on the inside of the chimney pot so that they can be identified if they ever go walk-about.

There is no need to line the flower pots before you use them for plants.

Right plant for right spot and your chimney pots sound great for succulents.

If you have some Crown top chimney pots,my husband made a wire circle to fit on top of the first ridge below the crown part..if you notice,there is a gap between the base and the decorative crown..He then made what I would call a cartwheel effect from the circle to the centre,with plastic coated wire,attached to the wire ring...I can then stand a plant pot to rest on it..and any water drains away..If the pot is a bit on the small side,I put an upturned plastic plant saucer in,to raise it up,so I can see the plant....I have never filled the chimney pot with anything,so I can still move it,or should I say,swivel it a bit,so I can sweep out all the dead leaves,and critters that hide..hope this helps..
I don't have any more,so I don't know if other types are the same design inside,to be able to do this...