Step 1: Things You Will Need in Hardware
2- A back cover for the mobile
3- 1/2 inch Foam tape
4- A scissor
Step 2: Things You Will Have to Do in Software
Go-To Settings>Developer Options>Activate Developer Options>Check Stay Awake>Exit
NOTE: Keep your phone on charging to use the stay awake feature.
To use a bright clock, you can download one from Google Play Store. In this Instructable I have used Giant Clock(downloaded from Play Store).
In this application there is an inbuilt stay awake option as "Screen Active" Hence, used here.
You can download and use any other suitable application if you feel like.
Step 3: The Back Cover and Foam Tape
Take an half inch Foam tape cut it and apply it on the Back cover as shown in the picture.
Remove the protective paper from the Foam tape & you can put on the cover on your mobile.
Now it's ready to be used as a wall clock!!
Step 4: Starting the Wall Clock.
Select a display colour for clock font.
Select any suitable background Image.
Check on Screen lock to keep the screen active.