I think L-girder is misunderstood. It is for me. I found an earlier thread about L-girder and after rifling through all the responses, I finally saw a picture of an L-girder without a whole lot of other structure piled on top and I still don't get it
An L or T or H or I beam is a concept to build with more than a specific table design. Those intricate designs you likely saw are both "show worthy" to an industrial level, and portable if needed.(2pc, folding base & top worthy of being called a platform) It will likely weigh many pounds less than a 2x4 slab too.
But just using the CONCEPT of the angle (L) in your own design can be a big step to this being a portable lifelong thing you could move more easily, and build off when you have the square footage to expand. You might need 2 more inches of storage thickness for each table top, but they wont warp on end either.
A skinny, but tall board like a 3/4 x 6 with 6 inch being vertical can support more dead weight than a more squared 2x4.
An angle added (L,T,etc) stops deflection across the horizontal plane, which is the 3/4" widths job. More efficient support out of less square inch with proper placement of the widths and angles. Even the top when attached right, adds rigidity with the angle where it attaches.
2" width is overkill for leaning forward on, and 4" is a bit shy for supporting weight. A 1x6 or even 3/4x8 is a better side frame, for mounting things, and runner structure too.
The support leg in the middle can be skipped if you run good 6-8" support the length of the table, near the center. To do that your normal runners will be shorter, more numerous,and staggered slightly for easy assembly.
L legs can have less X bracketing, maybe none, or the braces might sit higher on the legs leaving a more open side area for accessing the underside.
The L legs are no more difficult than a 2x4 to attach or remove. Folding hardware likely fits both. A plate, or wood can be added for wheels, and wheels with plates can usually be used attached at just three points.
You might save money on short screws vs long ones. But a predrill might be a necessary evil on the skinny wood, but the quality is worth it.
Two 1x4s in a T or L is also much stronger and warp free than the single 2x4.
Insist on 2x4s? Keep to 4' or smaller tables, -12” max space on runners, braces everywhere.
The 2x4 may B quick & easy. I've done it myself. But the wood was free.
If I spent a dime on wood, it would have to be four sides of 6-8" x? ..,.. The rest would be nit picky, but you sort of asked what the best way is, not how to "get-er-done".
Rich kept it simple, the images made it look hard. It's more work, but not "hard" and the result is so much better. The fact he chimed in should be a something to really consider. HW might have SOME experience outside of the real thing. Chris agrees, and I'm ready to write you a book..,... Look at the L girder again.
Just for fun, assemble an L from scrap, bang it around, throw it, maybe even park your econo car on it; but see if it changes your mind. Glue helps, but screws alone should impress you.
Or Flip a couch or chair over and you'll see angles used. Inside a wood TV cabinet they glue short runners, to the center only, to stop bowing there, etc.,etc
