Ok, here is where I got my desk.
http://www.pionet.net/~tomcox/catalog.htmScroll down to where it says Roll Top Desk Kits and you will see the one I made. At the time, he did not offer the large roll top desk kit or I would have gotten that one. One of those things, "Now he does it

." I was trying to modify mine to that type of desk. Oh well.
Anyway, I got the oak flat panel version. The desk is mostly a tongue and groove construction. The parts come precut with some fitting on the tongue portion of the joints. Mine was slightly fat in portions. Simple process to just thin the tongue to fit the grove portion. The desk came by UPS in 4 heavy boxes. The UPS driver just loved me. You do not need any fancy tools. You do need a lot of bar clamps. I borrowed several from freinds to supliment mine. Make sure they are big. I replaced a couple of pieces of the inset panels (the one in the back of the hole where the chair sits) because I wanted oak on both sides. The kit only came with oak on one side of the plywood. The only plywood is in the recessed panels, all the rest including the actual desk top was solid oak. This must be common practice it seems not to have oak on both sides for the pieces in the back of the chair hole since my moms desk is that way. Hers is stained in a dark stain so it does not show. I did not realize it for 20 years until I really started to take a look at it to compare it to mine. So in that sense, a table saw is nice to be able to cut your own pieces if needed.
Things I modified, my desk has two large drawers on the bottom. It looks like two individual draws but it is actually one large one on each side. The desk as it comes only has one. I put some vaneer to cover up the slots that would show along the inside of the one side to hide some slots that I did not use. The drawer glides are wood glides that come with the desk kit but I changed those to some undermount ball bearing glides. I even got some small ball bearing glides for the small pigeon hole drawers. I hate it when you pull out a drawer and it falls out, with these glides that will not happen and the drawers will always pull smoothly.
On the top, I changed it so it can be removed easily. I drilled some holes in the top and put dowel (oak) in the botom of the top unit to fit inside the holes. The top is then just held in place by its own weight. The way the kit comes, it is screwed down to the top and the the top is screwed down to the bottom drawer unit. If you do it by the instruction, you will see screw head if you happen to look from the bottom and even a little bit from the side. I did not like this, so my way you will not see any screws from any direction. I know this is picky, but as Al Rabe once said I have OCD. He is right.
The very top of the top I put on using dowels instead of what I would call a wierd method of using cheap wood and screws. Dowel locator pegs are really nice. If you do not have them, you cannot do what I did.
P.S. I know this looks expensive and it was but I figure this thing will go up most likely in value over time. It was however a LOT cheaper than getting one from a furniture store of this size and quality. It was also quite fun to build and a nice change of pace. Not to mention, it is fun to see peoples faces when you tell them that you made it. The look on their face: Priceless