Hinges for concealed door?

[foxhole]

Pivot hinges, such as https://www.screwfix.com/p/-/3651p
The part of the door between the hinge and frame goes inwards when the door opens out, so you will need to accommodate for that in the design of the door and frame.
Totally invisible when door is closed, and will also carry a substantial weight if required.

Don't have room to use these, bottom step is only 40mm behind where door will sit.

 

[StephenStephen]

Don't think they will hold as door and frame are 18mm mdf.

Yes - minimum door material thickness is 19mm for the smallest SOSS, I believe. I suppose you could glue and screw an additional wooden strip up the hinge side of the door, but that would seem a bit of a bodge, maybe?.

 

[foxhole]

Yes - minimum door material thickness is 19mm for the smallest SOSS, I believe. I suppose you could glue and screw an additional wooden strip up the hinge side of the door, but that would seem a bit of a bodge, maybe?.

Even with it,it would not allow for an overhanging frame on the hinge side.