A laptop on the dining table works for a week. After that you want a surface that stays put, a chair that is honest, and a background you are willing to be seen against.
A fixed desk needs 1.2 by 0.6 metres
That is enough for a monitor, a keyboard and a notebook, and it is the point below which the desk becomes a laptop shelf. Plan it as a permanent piece of the layout rather than an item of furniture, and it takes almost nothing from the living space.
A wall-hung top with a cable tray underneath keeps the floor clear and lets a proper chair tuck away. That chair matters more than any other purchase in the house if you sit in it forty hours a week.
Light from the side, never from behind the screen
A desk facing a window puts glare on the display; a desk backing onto one puts the window behind your head on every call and turns you into a silhouette. Side light solves both, and a rooflight above solves it better.
Add a task lamp with a warm output for winter afternoons. The overhead light that suits cooking is not the light that suits a screen.
Connectivity is a site question, not a house question
Check the fixed-line and mobile coverage at the plot before you commit, not at the nearest village. A rural plot with one bar of 4G will not carry a working day of video calls, and no amount of specification inside the house changes that.
Where fibre is not available, a fixed external antenna and a router with an external SIM usually beats a phone hotspot by a wide margin. Route a conduit for the antenna cable at production.
A door is what makes it work for two people
One open volume is fine until one person is on a call and the other is not. MD 3's closable ground-floor room is the model that suits a household where somebody works from home most days, and the partition needs mass, not just a leaf.
Where a door is impossible, a level change and a screen give some of the same benefit. It is a poorer answer, but it is a real one.
Sockets and network at desk height
Power at worktop height, a network outlet beside it and enough sockets for a monitor, a laptop, a lamp and a charger. All of that is a drawing note before production and a trailing extension lead afterwards.
Add one socket you think you will not need. It is the one you use.