I'll start by admitting I didn't do a great job photographing every step, but that's partially because this was a custom job for my friends, and I wanted it to be a one-of-a-kind piece, so I didn't upload plans like I normally would.  The top is built in three sections for transportation and convenience.  The top pictured is one of two that creates the top of the T.  It is 3/4 walnut ply, cut to 23" in width and 56 inches in length.  The frame is walnut, cut to about 1" thick with a 1" rabbet on which the table top rests and is glued to.  This makes the desk 24" wide by 57" tall.  

On the mitered corners, to add some strength, I decided to put some splines.  I clamps these two scraps to the table top, then used my biscuit joiner to cut a spline into the miter.  Two splines on each corner.  

I took some walnut and planed it down to fit snugly into the splines; about 14mm or so.  Glued in place.

Picture of the splines after flush cutting and finishing.  I got the finishing steps from this article, finish #1:  https://www.woodworkerssource.com/blog/woodworking-101/tips-tricks/heres-a-secret-to-a-better-wood-finish-on-walnut/

Drawer faces in process.  I know the opening to my cabinets is 25.5" tall, so I am opting for 26" of total drawer face, leaving a quarter inch overhand on the top and bottom.  

Planed, sanded, awaiting the finish.  

Plywood cabinet boxes built using general dimensions from this video.   I decided to add a back, get rid of the top (since it will be covered with the desk top) and add a piece of support to the top of the front as well.  Additionally, instead of trimming it out with lumber, I edge banded the plywood with walnut veneer.  

Here you can see some of the pockethole screws.  I tried using a knock-off from Amazon, but had really bad results.  The lock ring was loose, and even when it wasn't loose, the depth on the holes was too deep and the points of the screws poked through.  Kreg K4 to the rescue!  Well worth the extra cost, worked like a charm.  Drawer slides are from Rockler.  

Half inch prefinished ply for the drawers, with a 1/4" groove for 1/4" prefinished ply to create the bottoms.  The Kreg Microjig was a lifesaver here as well.  I modified the plans from the video so that the screws would be on the face (which will be covered by the solid walnut front) and on the back, where they won't be seen.

A look at one of the cabinets after completion.  

The final product, assembled!  Metal L brackets on the corners where the parts join, and I simply plywood box built to add extra support on the back.  Metal brackets sit inside the file cabinet and screw up into the plywood to hold the top down.