About 10 years or so ago, I built what I considered a premium CC sled. When I finished, I had what I sought to build. However, 10 years down the road you tend to view things a little differently. The sled I biuld, to this day is rock solid, performs beautifully and does everything I could ask of it. Not bad ya might say....but, sometimes more is not necessarily better. The more bells and whistles you add, the more weight you add. Bigger is heavier (typically, especially if your using standard materials) Esthetics do not necessarily add to functionality!!!!! I tend to like to build jigs that look cool, but that doesn't mean that work any better than one built to bare bones standards. Consider carefully application and practical usage.
IMHO the foundation for a really good sled has got to be Baltic Birch ply. Second choice would be a really good sheet of oak or maple ply. Just not a big fan of MDF for this kind of application. And certainly not particle board. Longevity is always an issue with shop built jigs and i just don't see either material holding up after a few years of use. 3/4" plys work great, but there is always the weight issue. If its just a small sled, then it probably won't make that much of a difference, A medium to large sled, it'll start adding up quickly. Most of the assembly can be handled with good screws. 1/2" ply works great, ya just gotta be careful when installing T-tracks etc.... 1/8th inch isn't much to hold a screw. I prefer to go with an epoxy on 3 sides to hold tracks in place. Pretty much eliminates any flex. Dado fences into place, don't use butt joinery. .....The very best advice I could give would be to just build one. See what you like, don't like, what works for ya, what don't and consider how to improve upon the design... then build the next one based on what you've learned.
Here's a link to one of my sled builds.. https://www.routerforums.com/twoskie...scut-sled.html