Plenty of bedrooms have no room for a table beside the bed. A mattress against a wall in a box room, a bed under a window, a headboard that meets a wardrobe. The clock still has to live somewhere, be readable at three in the morning and be reachable at seven. There are four workable answers and one that everybody tries first and regrets.
A clock on the carpet beside the bed is knocked over, kicked, unplugged and eventually stood on. It also fires its display straight up at the ceiling, which lights the room far more than the same clock at eye level. If you do nothing else, get it off the floor, because almost every alternative is better.
Mounting a clock on the opposite wall solves the surface problem entirely and has a side benefit: you have to look up rather than roll over, which discourages the two in the morning time check. In a rented flat, a small adhesive fixing or a picture hook is usually enough for a light clock. Silent movements matter here, because a clock on a bare wall in a small room is more audible than the same clock on a shelf.
A floating shelf a hundred and fifty millimetres deep, fixed at roughly mattress height beside the bed, gives you the clock, a glass of water and a book for the cost of two brackets. It takes no floor space and it stays out of the way when you make the bed. Compact wooden clocks of the kind sold by JALL fit a shelf like this without dominating it, which is more than can be said for the average bedside radio.
Wherever the clock goes, the plug has to reach a socket without a lead running across the floor where someone will walk. Measure before you buy, because supplied adaptor leads are often shorter than you expect and an extension across a bedroom is both ugly and a trip hazard. A battery clock removes the problem entirely, at the cost of remembering to change a cell once a year.
Anyone who hits snooze three times has an argument for putting the clock somewhere that requires standing up. In a room with no bedside table you are being pushed towards that arrangement anyway, so take advantage of it. The walk across a cold floor finishes the waking that the alarm started, which no additional volume achieves.
Whatever position you settle on, check the room in full darkness before deciding. A bright display at the wrong angle throws a glow across the ceiling and turns a dark bedroom into a dim one. Either angle the clock away or choose a model whose display can be switched off completely, which in a small room is worth more than any other feature.