Slates are good for using in edit to know what scene you are on. If you don’t have timecode it helps a lot. As for what to build. You don’t need the clapper part unless you are recording sound on something other than your tape. you can buy them cheaply these days. Info you want really is more about the show than the director DP thing which is nothing more than vanity. I would say take, scene, and notes are the three most important things yo need to see. YOu can buy a small dry erase white board form staples. 12×12 is good or 9×9 if you can find it. Then you can write what you want on the board, or put some permanent stick on letters for scene, take, etc.
Here is link for a slate I found in a search. It’s black and takes chalk but for $5 you can’t beat it. Look on Google under Movie slate or video slate.
http://giftmania.com/g/k/key.html?keywords=slate
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