So! Starting with your form intersections, you're doing fairly well in a number of places, but there are a few that definitely stand out to me. For example, the intersection between the cylinder and cone here don't take into consideration the curvature of the cone. Also the intersection between the sphere and box below is following the right kind of thinking, but just came out way too shallow to reasonably follow along the surface of the sphere. Always remember that the intersection lines you're drawing run along the surface of both surface simultaneously.

Moving onto your object constructions, you're definitely headed in the right direction and are applying a lot of the core principles well, though there are some hiccups worth pointing out. I definitely think you've progressed a fair bit over the course of the lesson though, and most of the mistakes are more focused towards the first few.

First one that jumped out at me was in your lava lamp, specifically with its ellipses. All but the rightmost are pretty well aligned to the minor axis (the far right is a little slanted), but the key problem is that the degree of the ellipses does not appear to shift wider/narrower as we slide along the object. Remember that as we slide farther along a cylindrical form, the ellipses will get wider as shown here.

Next, for your phone stand and in your nintendo switch, the importance of being able to construct solid boxes. At a glance, the phone stand's base box appears to be a little bit off - the far back plane seems to be slanting slightly, or perhaps a little too tall, and the piece with the G on it (which was honestly drawn pretty nicely) seems to tilt off to one side. Obviously the initial box we put down carries a lot of weight, and we're not always going to get it right, so I'm still glad you pushed through to completion. In the case of the stand, starting out with a larger more encompassing box would have likely allowed you to determine exactly where the top of the piece with the G on it should have been placed (since the way you did it was more arbitrary, leading to more guesswork), but you'd still definitely have been open to drawing that initial box to be a bit skewed.

Looking at the switch, one thing that jumps out at me are the buttons. For the larger thumbsticks, it's important to construct them around a central minor axis (establishing a cylinder and then breaking that down into the more specific forms). This helps us avoid making them lopsided. Additionally, I'd strongly encourage you to take advantage of capturing the shadows your forms cast on their surrounding surfaces, as explained in Lesson 2's texture section (which was rewritten to be clearer at the beginning of February). This would be considerably more effective for some of the smaller buttons, where you didn't have too much room to capture their internal details - so actually doing so results in clumsier forms. To this point, focusing on cast shadows instead can capture the same information in a manner that doesn't feel as clumsy.

To this point, remember that we don't just fill holes/gaps in with black - those black shapes should still correspond to cast shadows, so cases like the power bank's ports should not be entirely filled in. Instead, you should think about how the outside forms are casting shadows into the hole - this means that at least some of the side of that hole will not be in shadow.

As far as construction goes, I was quite pleased with the computer mouse you did at the end. It definitely showed a lot more patient, careful breakdown of your forms and you managed to achieve quite a complex object using those techniques.

All in all, I think you're applying construction well, but there are certainly areas where you're taking shortcuts (like the nintendo switch's thumbsticks), and all in all, you do need to continue working on freely constructed boxes, but all in all you're headed in the right direction. As such, I'll go ahead and mark this lesson as complete.