How to make a box pouch / without bias tape DIY

How to make a box pouch to make a gusset by sewing a bag ✨
It is easy to make because there is no troublesome bias tape processing ♪
Since the gusset is used as a return opening, it is easy to turn it over if it is made of a thin cloth.
Have a nice handmade time 🍀🕊️
[Finished size]
W 12 cm H 8.5 cm gusset 6 cm
○ Outer fabric / Lining/ interfacing
W23 cm x H16 cm, 2 each
○ Tab
8 cm x 14 cm 1 sheet
○ Zipper 20 cm