Use crafting table (F)
click on planks and move to slot on crafting table
hit control to drop a plank into a slot and whole stack drops
Can't drop only one at a time
Only way to put planks in more than one slot is to drag stack across several slots whilst holding down mouse button (distributed evenly)
Tried checking controls in options: checked LControl assigned to pick blocks but that wasn't problem anyway
saw advice to hold F3 +C for 10 seconds, triggered debug crash
this has only happened since downloading 1.6.1 so presumably reset controls but can't work it out