We have a sewing basket set out for my son (who is now 6 but we've had it out since age 4) with felt sheets, some thicker needles, and embroidery thread. It wasn't long before he could thread the needles himself and he continues to go to that basket all the time when inspiration strikes to make little pillows, bags, and such.
Also we have a generic "art basket" accessible with modeling wax, beeswax crayons, Lyra pencils, and plenty of fun papers. That gets used every morning without fail and throughout the day too.
I second the idea of having him apply beeswax polish to things, sanding is good but can get a little difficult for little people after a bit.
We also have a basket of blank gnome bodies near the sewing basket, and DS often creates his own characters for play by fashioning some simple felt or fabric outfits for him gnomes.
And like you mentioned for more "planned" projects we bake (that is a sort of handwork afterall), wet felt, some needle felting though he's poked himself enough times that he's a bit wary now... candle making and other wax projects, beading, etc.
I really believe handwork is not emphasized enough for little boys, even in Waldorf families. Good for you, it will really be such a good thing for your little guy in the long run.
