I made some of those, no plans needed. Take a 2x4 and clean it up if needed, cut a square that's as long as the board is wide, then everything else is either twice as long, half as wide or cut on a slant for wedges so that all the parts will fit together in some similar fashion. Kids usually won't care too much if they're not 'perfect', they'll be perfect enough for them to play with.:icon_thum