This is a rather lengthy process that takes a lot of time and patience. I made the shell for this over the weekend by forfeiting having a life and I'm only about 20% done what I would consider a "finished product".
Here are my steps for building an Earth-like planet. May your creativity and sanity prevail; should you ever try this...
Step 1: Make the starting point: Place a station block, and set your plane symmetry on all 3 axes. That starting block is your exact center and the point where your layers (reactor, shields, stabilizers and various surface topographies) will emanate from. I find that "measuring" by using blocks extending in all six directions will help you decide just how big you want to make your planet and give you a decent idea of how big the radii of your additional planet shells should be.
Step 2: Decide on your reactor size: Set a spherical build helper on your center block and check the box that says "restrict building to helper". Set the size to something you can reasonably expect to fill with reactor blocks over the course of a game and still have room within a (512m max size) sphere to fit stabilizers and shields and to compensate for adjustments to QuickFire configs.
Step 3: Build the reactor: With your spherical build helper in place, use the fill tool to "place fill origin" within one of the helpers wireframe blocks. Set "blocks added per click" to maxium (I believe it's 5000) and then start using the "fill" button to fill the helper with reactor power blocks. You will end up with a hollow shell made of reactor blocks. Leaving the reactor core hollow will allow you to start the planet sooner and "level it up" as you gather resources. Use the fill tool inside your reactor shell to max out its power.
Step 4: Stabilization: Provided QF never reinstates stabilizer distance, repeat the process in steps 2 and 3 by creating a hollow shell of stabilizers around the reactor. Make it big enough so that filling it up will give you enough stabilization to support your reactor. Once again; you have the opportunity to start a planet sooner by doing this.
Step 5: Shields: If you're playing multiplayer, or expect to come under any kind of attack, I HIGHLY recommend that you build your third shell out of some kind of rock, hull or armor. Once that shell is in place, use the fill tool to add a clump of shield rechargers to fill it. Expand from that clump, ensuing that you haveonly one group. Repeat the process for the shield capacitors. Do not make the shell out of shield blocks themselves or just one enemy shot may trigger a shield integrity failure (which is not displayed anywhere in build mode) and cause your planet to start to explode;
1990s style. You can also add a shell of Adv. armor around that and thicken it as you gather resources if you want to be extra safe from deep penetrating cannons or beams.
Step 6: Surface level 1: Build another hollow shell made of any kind of rock around the outside of the entire assembly. Do not use this rock for any other part of your surface, as this will be the bottom of your surface topography.
Step 7: Surface level 2; Raised topography: Build yet another shell made of a different kind of rock than from step 6 that is 5 or more meters larger in radius (mine was about 8m) than the previous shell, then use the fill tool to fill it with the same kind of rock.
Step 8: Carving out your raised topography: Using the selection sub-menu in adv. build mode, use the "pick with camera" option to select the kind of rock used in step 7. Use whatever means available to cut away the step-7 rock and shape your continents, mountains, islands, etc. This is part HIGHLY tedious no mattter how you do it but I find that the use of a 3rd party tool such as "The fastest mouse clicker" or any other auto clicker app can make the process more tolerable for both your sanity and your clicker fingers. You can repeat this process (shell, fill, carve) as many times as you like to get varied terrain; similar to what we see in the Schine-brand of planets.
Step 9: lakes, oceans, rivers etc.: Make yet
another shell, composed of either water (to allow objects to submerge) or larimar (for better aesthetics) that is several meters less in radius than your step-7 shell. You now have a perfect ocean surrounding the planet while letting the land masses protrude through the surface of the water.
Step 10: Sandy beaches: Using the selection sub-menu in adv. build mode, use the "pick with camera" option on the larimar "water" and check the box that says "replace with active slot". Make your active slot either sand or lukrah, then trace the edges of your continents using the replacement tool with a block size ranging from 3x3x3 to 5x5x5.
Step 11: Details and inhabitable areas... This is best left up to the individual artist's tastes.
My previous version has some nice looking city effects that give the impression of a densely populated space-age planet and includes areas you can actually land on and visit.