If you haven't come across the Urban Jungle Bloggers yet, you need to. They're basically a community of bloggers led by Judith and Igor who celebrate all things green and leafy by posting to a theme each month. So this month's theme is to give a green gift. Aka the best gift in the world. Aka let's get tinning!
The cliff notes plus my hack version of the aforementioned tutorial is this: Buy some beans. Turn tin upside down and use a can opener to take off bottom. Eat beans or put into a container and keep in the fridge for later consumption (DO NOT WASTE THEM!). Wash tin and remove label. Put moss in the bottom (or top) of the tin so that the green is at the bottom. Cover with compost or a good, fertile soil then water. Stick removed tin bottom back on with hot glue. I actually used a thick piece of cardboard cut to size for the bottom because it seemed slightly less dangerous than handling the sharp aluminium disk.
I also kept it simple and skipped adding a new label as I prefer it nice and naked for display purposes. Finish with a little tag and make sure you gift it within a couple of days once tinned. Fun right?