hi everyone  
i'm going to make a concrete fingerboard park this summer and i think i'm gonna use a wooden base and fill wooden frames with concrete...

do you guys have tricks and tips? do's and dont's?

The best thing to do to build a tabletop foundation for a concrete park would be to build it inside a mold, like fiber cement tables are made. This makes it extremely lightweight and strong. That way there is no need for a wooden structure after molding at all..
 
Just make a simple square box the size you want the park to be and start spraying a thin smooth coat of very fine cement. After a bit of curing the fun part starts by adding patches of a fiber reinforced cement mix. Let it cure, remove the mold pieces and flip the thing other way up. Congratulations..you have now got yourself a lightweight fiber cement table top!
 
Cement obstacles can be made the same way and added to the table top. Get creative..
 
Youtube link that will help you on your way:
https://www.youtube.com/watch?v=hrT7Px8CLCg&NR

i get it with the thin base layer bot not whit the obstacle? i think i'm just gonna put concrete on a wooden platen and start shaping from the ground of an some frames to build a stairset

http://www.fingerboardhq.net/t7480-how-to-cement-pool Check this out!

https://www.youtube.com/watch?v=m5vwuPGuO-g Hope this helps

Those options of going about it are all ok i guess. But the surface will never be as smooth as a molded park will be + it removes the need to use styrofoam or simular all together. Just trying to make you guyes think in new ways and easyer ways of going about it and save a few bucks in the same go If you know what I mean..
 
I was thinking in the same ways before one time when I sat down at what I thaught was a solid concrete table outside a mall close to where I live. But after a closer look under the table I noticed it was actually under half an inch thick and super light weight for what size and how solid it looked. Do yourself a big favour guyes and look into this whole fiber cement deal. Its the business..

I have a14 foot concrete park that I put on a Formica and cabinet base in garage I already have workbenches so I skate on top and store underneath always Remember to be patient and test mixes with other things like Tupper wear also old hotel key cards etc work great for smoothing out and get a old handheld cooking mixer.