This is a Techies minefield sign magnet from the video game Dota 2. I printed it using brown, red, and white filaments. 

For those who need to manually set filament changes (like me), do the following:

• Set your first layer and layer heights to 0.2 mm
• Begin with brown.
• At layer 11 (2.20 mm), switch to red and insert your magnet
• At layer 21 (4.20 mm), switch to white

I like to iron the topmost surface, but that is a personal preference.