To continue the account of some of my childhood hobbies.
A speedy and cheap activity is loo paper Papier-mâché. First take sheets of loo paper (having checked you haven't taken the last roll in the house - you could find yourself rather unpopular) and put them in water. Put the soggy mass on a mould e.g. egg cup. Leave until completely dry and then it can be pulled off in one piece (well, it will come off in one piece once in every twenty goes and only if you are very, very careful). It can be painted with very, very dry paint - anything too liquid will destroy your creation. The resulting object will have a very short life - so don't imagine you will be making a family heirloom.
I also liked decorating things with shells that I'd collect on holiday. I would take an empty matchbox (one of the few advantages of being the child of a couple of chain smokers is a constant supply of match boxes), glue on the shells in patterns and then present the box to a delighted (possibly slightly glazed-eyed and bored) grandmother. Poor Nan - her bedroom often smelt a bit odd in the weeks after receiving these gifts as I rarely checked to see if the sea creature has left its home before I wielded the glue brush.