Please find the Cover Pattern with 3 layers + a space for a filter below :
All you need is :
-Sewing machine
-Thread
-Scissors
-2 x 22 to 25 cm elastic (0,5 cm wide)
-1 piece of fabric 37cm x 19 to 21 cm
-a ruler
-chalk for fabric or pen
-iron
It will take you around 30 mn to sew it.
Find the step by step through pictures below:
Final result 
Step 1 : trace the lines on the wrong side of the fabric 
Step 2: sew the 2 hems. 
Step 3: iron the 1 cm pleats as an accordion 
Step 4: pin the pleats and the 20 cm elastic each side. 
Step 5: fold top and bottom on the pleats right side against right side an d sew. 
Step 6: Turn the mask inside out. 
Step 7: Fold the mask in 2 and sew a 1cm wide dart on 3 cm long on top and bottom of the mask. 
Wear the mask 🙂
COUTURE NOMAD 