The major problem comes in under the understanding of the form of the particular subject that causes our brain to just wing it off

Yeah i can understand this, but in my opinion we can still wing it while maintaining a sense of volume or 3D, which may not be what we want but definitely far better than drawing lines or doing symbol drawing.

If you don't mind , can you provide some exercises to reinforce the process of clearly understand the structure present below the reference.

Drawabox in fact focuses a lot on this, so i can't really give you a better exercise from the ones that already exist in Dab, i mean if we go back to Lesson 4 and 5, Insects and Animals, its really all about understanding how those particular subjects are composed and then picking the most suitable forms to reproduce that particular subject, that's what in my opinion is understanding the structure of a subject (and like i said, this is literally what Drawabox lessons are about from Lesson 1 to 7).

Once you have a good understanding of the structure of that object you can then start to draw it out of your imagination, for example, how is a spider composed? I know theres 3 shapes, a circle, an 2 ellipses for the body, and sausages/cylinder like forms for the legs, once i understand that, i can then draw those shapes and transform them into forms (by either wrapping around, giving sense of the different planes of the object, etc) or drawing direct forms (things that have a strong sense of 3D, like a cylinder or a box) and then have a drawing of a spider, the same applies to an animal, i know that animals have a cranium, a ribcage and a pelvis, i can create an animal of some sort by knowing the components and how to simplify them (A ball, and 2 ellipses), and then draw those shapes, transform them into forms and then have an animal of some kind.

Will this drawings be perfect? Maybe not, but its the foundation towards understanding how those subjects are composed, then is only a matter of repetition, time and mileage that i will be able to hopefully create a better representation of the subject matter (and of course if we want to get deeper and more accurate, maybe at some point studying the anatomy).

Now, will this approach work every single time? I don't think so, i mean i particularly don't consider myself a good draftsman, i still have trouble understanding particular subjects, for example i absolutely have no idea how to draw a mantis, i know how to do the head, but the bodies are incredibly annoying, at that point i think its best to experiment with different techniques, either the ones provided by drawabox or different ones and see which one fits the structure better, but the key idea is to always try to visualize simple shapes and forms to be able to simplify the complex structure of the subject.

Outside of drawabox however, i don't think there is a definitive answer for this, i mean there may be a lot of exercises to focus on understanding the structure of a particular subject but ultimately it comes down to how you understand the particular object and how you decide to break it down, because there is a lot of techniques to draw a specific subject while still focusing on Structure.

Much better if you can point out some methods and techniques that drawabox teaches that comes under the topic of understanding the below structure of the subject

Well like i mentioned earlier, Drawabox from lesson 1 to 7 focuses of different techniques to approach understanding the structure below the subject, that is what construction is.

But if I had to choose, i would say the concepts from Lesson 2 to 5 are key to understand a good chunk of how we could use forms as opposed to lines or symbol drawing, because they teach concepts that are incredibly vital such as:

• Wrapping around objects.

• Adding Masses to forms.

• Lines and Things that flow in 3D space.

• A general sense to draw in 3D as opposed to flat.

tbh I don't really know the meaning of "Sit in 3d space"

I personally understand the concept of "Sit in 3d space" as how that objects exist in perspective or in real life, because when we are drawing we draw on a flat piece of paper and that sometimes makes us forget that the subject that we are drawing as depth and volume to it, and thats something we need to keep in mind when drawing, so for me "keeping in mind how that object sits in 3D space" means how we can convey that the object has depth and/or volume to it, to make it really feel 3D and not flat.

To wrap things up, like i mentioned to OP, the biggest problem with Symbol drawing is drawing flat lines as opposed to believable 3D forms, like for example, an eyeball is a sphere not just lines.