Good gawd, what is THAT? Well, definitely seen better days....
I haven't built a DS centerboard, but I've built two on other boats, and rudders (which are much the same). The centerboard drawing that you need is right in the DaySailer Assoc Bylaws:
https://forum.daysailer.org/pdf/dsbylaw3.pdfFigures 6.1 and 6.2. Read up on the acceptable weight (20lbs, I think) and all the other whys and wherefores - Rules 6.1-6.3. You'll want to stay class legal, so you can race the boat and easier resale. For your build, Rule 6.2: "The centerboard shall be of built-up or molded fiber-glass and resin material or of
wood covered with fiber-glass and resin" (emphasis mine). So you want to glue up a set of square strips, one on top of the other. The length of the strips go fore-and aft, 15" long, the width is just a bit narrower than your centerboard slot (measure it!). As GL says, alternate the grain of the strips for strength. Glue them up with thickened epoxy and then clamp them together with the appropriate long clamps. If you don't feel like building up a set of pipe clamps, then you'll need to build some sort of jig, no big deal. You'll wind up with a flat board, which you should then cut to the shape given in figures 6.1 and 6.2.
Now in theory you can leave it as a flat plate, but you'll have one hell of a slow and unmanueverable boat! You want to carve out at NACA profile - like an aircraft "fin". Do some internet research, but don't overthink it! A NACA 009 is probably just fine, in fact just having your max breadth 1/3 of the way back is fine. You WILL NOT be able to make a true NACA razor-think trailing edge, so just round it. There's even some hydrodynamic theories suggesting a square trailing edge! I'm not advocating a square edge or anything else, just saying that you should do some research and thinking, the rules give you some freedom. My personal favorite for this kind of carving is an angle grinder with a flap disk and then a small belt sander. Cut your NACA profile into a piece of plywood to use as a guide. If you have a drill press, you can drill yourself guide holes to appropriate depth. Otherwise, just scribble a pencil over any "high spots" then grind them off. Practice on some plywood!
Lastly, you'll want to cover your wood fin with fiberglass cloth and more resin (ideally epoxy). This is an art all to itself, probably the hardest part. Do some research, watch some videos, read on this forum, ask questions. Remember you'll have to subtract the thickness of your cloth and resin from the centerboard width. In other words, if your CB slot is 2 inches wide, you want a 1.75 inch wide CB, but the glass is .125 thick, so you want a 1.50inch board + .125x2 for the glass (made up numbers)!. You know the drill, measure twice, cut once. And don't forget that you want a smooth surface, so you need to fill in the grain of the cloth, put a bit of extra epoxy on top of that and then sand it back down....not easy! But we have several fiberglass experts on this board, so just ask (and do some test runs on scrap wood!). And it may be overkill, but I sanded my own fin all the way down to 3000-grit wet. Over that IS overkill though, there's only so much perfection you can get by hand. Wax it and call it a day - or don't wax... now we're getting into personal preferences and "art." Most of all, have fun! There's something very satisfying about building you own boat stuff - pride and accomplishment.
All the best!
Tom
P.S. Epoxy poisoning is real! During both layup and sanding, wear gloves, wear long sleeves, wear a mask, preferably something like the 3M 7500 series. The $40 I spent on my mask are the best boat-work investment I've ever made. Epoxy wont "kill" you immediately, the poisoning comes on as an allergic reaction over time - nasty hives and prickly skin, headaches, cold sweats. Avoid it by taking care of yourself. I don't mean to scare you off, just want to save you from having to work epoxy in a veritable bio-hazard suit like I must nowadays. Ounce of prevention, worth a pound of cure!