To answer your question first, in Lesson 7 I explain a specific process for building down a unit grid, which starts by using the technique explored in the cylinders-in-boxes (using an ellipse to draw a square in 3D space) and then flipping it to the other dimensions. It is quite complex, which is why I don't introduce it until we really need it. For this lesson, I'm fine with students eyeballing their proportions. It is certainly a skill that develops through practice, specifically in the construction of objects like this rather than just practicing boxes.

As for making your boxes more isometric (technically you mean axonometric - isometric is a type of axonometric projection using very specific angles), it is definitely important to always keep in mind that the lines of your boxes are meant to be converging, even if only slightly. The awareness of this fact helps us avoid the kind of awkward parallelity and divergence we can end up with otherwise, even if the different is fairly subtle. So just be sure to think about that when drawing those lines, rather than aiming to actually keep them parallel on the page.

Outside of that though, objects of this size should have very minimal foreshortening applied to them, so it's not particularly far off to have them be so close to parallel.

Honestly, overall your work throughout this lesson is quite superb. I have a couple minor suggestions to offer, but all in all you've been extremely fastidious in breaking down your constructions with subdivision to find specific positions for all your little geometric features. This has helped maintain a strong illusion of solidity in each object.

One very minor point I wanted to call out is the angle at which you apply your hatching lines. For example, looking at the stapler, the hatching lines run slightly diagonally across the surface upon when they're sitting. This was definitely unintentional, and it has the ill effect of confusing the viewer in terms of the orientation of that plane. Instead, aiming to keep them more parallel to the plane would definitely be better. Since our objects are all very small, we don't need to worry about the vanishing point with this - just keeping them more parallel/perpendicular to the actual edges of the plane is enough.

I'm a little confused by your orchid pot - specifically the little triangular cut-outs. While the outermost side of the pot has clearly drawn triangles, I'm noticing that the inner side of the cut-out doesn't actually match. It seems the edges that should be angled (to form the top part of the triangle) are running more or less straight up/down. Is this intentional, and part of the actual physical pot?

For your camping mug, I actually have a demonstration that'll help you better grasp how to build the handle. Basically whenever possible, start out your constructions with boxes and straight edges. Lay out the overall structure of it, and then when it's done, you can start rounding it out. This also goes in hand with the "specific curves" principle explained here. The only type of curve you can generally skip this with are actual circles/ellipses - but even then, it doesn't hurt to use a box to situate a particularly difficult cylinder.

So! With that, I'll go ahead and mark this lesson as complete. You're doing great, so keep it up.