A very low cost and very easy project anyone can make, great activity to get your kids involved in as they are soooo proud of making a quality gift that looks like it was professionally made.

All you need is the following

Materials:
Reclaimed slate tiles 30p each (reclamation yard, ebay, old roof)
Wood batons £ free (scrap wood, off cuts or DIY store)
Screws 30p

Total cost = £2 - £2.50 per pot

Tools:
Ruler
Saw
Screw driver
Drill + masonry or tile drill bit + Screwdriver bit

Step 1: Drilling Tiles

Stack four tiles on top of each other, ensuring the nail holes and edges are aligned
Measure and mark three holes for the screws (the nail holes count as one hole)
Drill through all the tiles at once, be careful not move the tiles whist drilling. If they do move realign them immediately

Step 2: Cutting the Wood Corners

Measure the distance between the bottom of the tile and the top hole, now add 20mm
Cut four wooded batons to the measurement above

Step 3: Cutting the Wood Corners

Measure from the bottom of the tile to in between the first and second holes (see the photo for clarity)
Mark this onto each of the four batons and cut

Step 4: Assemble

I use Torx screws just because i think they look cool, any wood screw is fine though :)
Ensure the wood is aligned with the edge of the tile before screwing in place
Attach two batons to one tile covering the top and middle holes, this leaves the bottom home exposed
Repeat on another tile

Step 5: Assemble

Put the assembled tile on a flat surface
Take a unassembled tile and align it to the edge of an assembled one
Screw in place
Repeat so you have two 'L' shapes

Step 6: Assemble

Bring the two 'L' shapes together and screw together

Step 7: Adding the Base

Turn the pot upside down and add a slate to the inside
You might have to cut the slate to size, there are three ways to do this, none are suitable for kids to do so adults only!

Old School Method

Get a machete or thin strip of steel (2-3mm thick)
Place the tile on a flat surface with a straight edge
Smash the hell out of it :) (see video)

Quicker Method

Use a diamond blade in an angle grinder
Cut tile

Neatest Method

Get a wet blade tile cutter
Cut tile

Step 8: Fixing the Base

Bolt the small pieces of wood in place
Turn over and admire your new pot :)

Step 9: Filling

If you have made a large pot it would take a load of soil to fill and be soooooo heavy you would need a JCB to move it

Solution

Use old water / milk / fizzy drink bottles and neatly stack in base. This is good for a number of reasons it resuses a waste product, makes the pot significantly lighter, and increases drainage
Fill the middle with garden shreddings / grass cuttings / plant trimmings. This saves much money on compost :)
Add compost to the top layer.