Therefore, in order to avoid using a 3rd-party software, next best method of approach is to turn a folder into a mounting disk image.

Steps to protecting a folder
Steps to increasing capacity of new disk image

Step 1

Open “Disk Utility” application.
Location: Applications → Utilities.

Step 2

Choose: File → New → Disk Image from Folder
Shortcut: Shift + Command + N

Step 3

Choose a folder to protect and press [Image]

Step 4

Choose a location to save the disk image
Select “read/write” option for Image Format
Select “128-bit AES encryption” option for Encryption and click Save

Step 5

Type in a password.
Click Key icon for more password options. (optional)
Uncheck “Remember password in my keychain” and click OK.

Step 6

Navigate to the location of saved disk image.
Double click to mount the disk images as a Volume.

Step 7

Drag-and-drop files and folders within the protected disk image.

Default size is 9.2 MB.
To view: click item, choose File → Get Info.
Shortcut: Command + I

Step 1

Open “Terminal” application.
Location: Applications → Utilities → Terminal.
Type: hdiutil resize -size 100m (where 100 is your assigned amount of space. Do Not press [return])
Drag-and-drop your unmounted volume into the terminal.

Step 2

The output should look like this: hdiutil resize -size 100m /Users/myusername/Desktop/myFolder.dmg
Now press [return])
Type in your assigned password. (password area will remain blank for security reasons. Do not fear. The system is reading it. Press [enter] once done.)

Step 3

New Default size is 100.2 MB.
To view: click item, choose File → Get Info.
Shortcut: Command + I

To exit the terminal, type “exit” without the quotes and press [return].
Choose File → Quit.
Shortcut: Command + Q

~ the end