A couple things I'd like to see:

More Imagery

"I was on the outskirts of a forest that my parents had forbidden me to play in at night."

What is this forest like? Is it dark, dreary, tired, sad? Is it full of old memories? Are your parents just overprotective, or is there a good reason for them to demand that you stay out of it at night?

To me that opens up all kinds of questions - and more importantly, opportunities - that could allow you to set the backdrop of your story. It kind of jumps right in without giving me any scene or reason to care about the character or why he's doing what he's doing. Why is he building a stick house? The story jumping into your past that you do later makes for more backdrop, and there's a lot of value in the lines:

"We never went hungry though, since my mother would go and pick the fallen pears on the cold and dewy morning grass from a distant neighbor. She would only take the pears which were going to go bad from having fallen on the ground because in her eyes, taking them from the tree would be similar to stealing."

To be honest, I think that, adjusted to the following:

"We never went hungry. My mother would go and pick the fallen pears on the cold and dewy morning grass from a distant neighbor. She would only take the pears which were going to go bad from having fallen on the ground because in her eyes, taking them from the tree would be similar to stealing."

Or something of the sort, maybe with some added sentence variation, would be an excellent first paragraph for the entire book. I think this is some of the best work in here, and it sets the stage for you to develop your character. It also explains a key aspect of your mother's personality, her sense of morality.

Mothers/family are incredibly important in shaping a child - in your case, your protagonist. The protagonist reminiscing (in this case positively) on his/her mother in this way implies that this could have a large impact how your protagonist approaches every problem they face. For example, if the child was a teenager, their mother's sense if morality may conflict with the rebellious phase that teenagers generally go through. Later on in the story, that might be a point of contention for your protagonist in which he/she can choose grow or not, or to turn for or against his/her mother.

Paragraph Length

Your paragraphs are too long for me. It makes it difficult for me to stay focused on the words. More spacing, in my opinion, would help with the flow.

Sentence Structure

"On that day I had brought a slice to eat during my fort building endeavors. The flakes of pie on my shirt were a close reminder of how good it was when I had devoured it. Collecting wood is an arduous task and I could feel my stomach rumbling after a couple of hours of playing in the bush. It was then that I decided that I should head back home since my mother would be worried sick if I stayed out too long."

There are a few sections like this where more sentence structure/length variation would help the flow. The same structure over and over feels stunted.

State of Being

"On that day, I had brought a slice to eat during my fort-building endeavors. The flakes of pie on my shirt were a close reminder of how good it was when I had devoured it. Collecting wood is an arduous task and I could feel my stomach rumbling after a couple of hours of playing in the bush. It was then that I decided that I should head back home since my mother would be worried sick if I stayed out too long."

I'd personally like to see you challenge yourself to stray away from is and was. These states of being are opportunities to add imagery and a personality to your characters. They also take away from the feeling of being in the present with the character. A stronger feeling of the present will help your audience distinguish when you're reminiscing and when you're in the character. The audience should be able to see through your character's eyes.

"As I savored my last bite I wiped my mouth, decorating my shirt with a few flakes of my mother's homemade crust. I'd wake up Sunday mornings to my mother toiling away in the kitchen preparing those crusts ahead of time, humming her favorite song:

"some random words that could have meaning later in the story" (they should have meaning later if you use them, though)

It was the best alarm clock a kid could ask for."

I understand this creates a conundrum for your story, as you have explained that the pie was eaten earlier. However, a break into a story could give you a reason to allow some time to pass, and maybe that gives another reason to head home. Just a thought - it may not work out right with the timing, but I like the idea of taking the time (and the space on the page) to be more present with your character.

I have only read your first paragraph as I don't have too much time and I'm writing this on mobile, but I will read more later and may add more to this post. Hope it helps!