by cutting, i assume you have a deck and just want to cut out a new shape ?
first start off by drawing a centerline all the way over your deck, then take a pencil and draw the shape on one side of the deck, then take a ruler and measure every cm/ inch from your shape to the center line and copy it towards the other side, once this is done on a good amount of spots, connect the measured dots with a fluid line and you should get a pretty decent symmetry...
you can also use a large paper sheet to draw out your profile and simply flip it around onto the other half to get perfect symmetry ....
anyways, once you have your profile, take a jigsaw (powertool) and simply cut along the lines, when this is done take a file and some sandpaper on it to round off the edges and make the thing feel smooth !
now to make it really good, spraypaint your board or put a clear varnish over it to protect the wood from the elements.
mount up your trucks and you're ready to go !
some small notes, make sure you have room for your wheels, you have 3 options, you make cut-outs for the wheels, you grind out wheel wells (check silverfish for tutorial/tips) or do nothing at all ...
in the last 2 cases you'll have to use risers to adjust how high your deck stands on the trucks....