Charcoal, 35 bytes

ＵＯ⁶⁰¦²⁴”|⁻ＰＨ”Ｆ³«Ｊ⁰⁺⁴×ι⁸×⁴⁺×⁶”|‖▶Y”¶

Try it online! Link is to verbose version of code.

Explanation:

ＵＯ⁶⁰¦²⁴”|⁻ＰＨ  - drawing a 60 by 24 box with background being /////\\\\\
Ｆ³«            - loop 3 times: 
Ｊ⁰⁺⁴×ι⁸         - Ｊ⁰⁺⁴×ι⁸ jump to line 4+i*8
×⁴⁺×⁶”|‖▶Y”¶     - essentially printing the reflected pattern 4 times which would overwrite the next 3 lines as well
 

Optimizing: