to
Step 1:
Open up the base
Step 2:
Click on the rounded rectangle tool
Step 3:
Make sure the settings are as so.
(Note : You can change the radius size if you like)
Step 4:
"Draw" a rounded rectangle on the image. Make sure it covers the whole image.
(Look at picture if you're not sure)
Step 5:
Go to "paths" and click on the button that is boxed in the picture above.
Step 6:
Go to "edit" and click "copy merged".
Step 7:
Create a new "layer". 100x100.
Step 8:
"Edit" and then click "paste".
After that delete the "background" layer.
Step 9:
Save your image as .png
Step 10:
Lastly, choose interlaced