Gears 5

Updated solution to add thumbnail before playing your created map instead of after. June 3rd 21

This achievement is for creating your own escape map.

From the main menu, go to:

'Multiplayer'
'Escape’
‘Map sharing’

Press to go to ‘My maps’
Then select create new map.

You’ll want to make the map as short as possible.
Making it longer is optional if you actually fancy making a decent escape map for you and your friends to play.

Select and a build a start tile (should be top option out of the 3)
Place the start tile anywhere you want.
Then select and build an escape tile (bottom option)
Place it above the start tile.

After that is done press start and edit Thumbnail
Press to capture thumbnail and confirm

Now after that’s done select ‘play map’
You have to play your own map first before it can be published. Once played on, return to editor.

Nothing else is needed now once all boxes on the right hand side are ticked.
You can customize the description and add tags if you wish.

Press publish to finish off.

Once published your achievement shall unlock

Other guides didn't work for me so here's how I got this cheevo. On the main menu select Multiplayer, Escape then map sharing.
Once in Map sharing press RB to go into My Maps and select Create New Map.
When the map creator page opens up you need to select a start block which will be the first block on the left of the screen, select it and press A to place it. Once its placed ther'll be a red square with a hand in the centre on the block you've just placed so move that square off to the top of the block until the hand changes to a spanner and hammer, Press A, this will bring the room selection menu up again.
move two blocks down until the Escape Exit is highlighted and press A to select it, move it until it's white and connects to the start block and press A to place it.
Press RB to go along to pickups and add a few of your choice on the start tile near where the tiles join.
Once placed press the menu button to go into the diting page and head down to Map Thumbnail (can't publish the map without one) and press A. This will bring up a picture that you just need to press the double square button to capture.
Once the thumbnail is done highlight play map on the menu on the left and play your map (it'll ask you to save it before playing so select that.)
Once you finish playing the map select Return To Map Editor to be taken back to the map building page and press the menu button to go into the editor page.
If all the Map requirements on the right of the screen are ticked then select publish in the left hand menu and the cheevo shoul pop when the bar on the top left has filled.
Once the cheevo pops you can use the same method to start the map to delete it, Multiplayer, Escape, Map sharing, My maps and select your map go down to delete and delete it and then you can spend some time building a more elaborate map if you like.

Mode discontinued, the achievement is set to auto unlock after signing in to the menu after booting the game.

Simply load up Gears 5 in Cloud Gaming, or install the latest version of the game/title update, then navigate to the main menu and the achievement will then unlock.