Manufacture:
Start with the largest pair of Docs or army boots you can find. Make the shape of their internal space in, say, tungsten, with brief steel members sticking out at the top for connection to the driving mechanism.
People are mostly water. Tungsten has about nineteen times the density
of water. Thereby we can fit approximately the entire weight of a man into his boots.
Modify the soles, so that the tread makes a distinctive pattern. The pattern might incorporate a trident.
The mechanism is two-fold.
One element of it, possibly involving a pair of off-centred wheels or a short camshaft, makes the boots walk. I say "walk", but it would be a sort of mincing shamble, with a very very short "stride", there being no actual legs to speak of. Unlike proper walking robots, we wouldn't have to worry much about balance, because the centre of gravity of the whole assemblage is so low.
The other element, usually dormant, drives a side-to-side shaft with a broad but light pad at each end. This is able to deliver a swift shove to right the machine if it gets turned on its side by, say, an explosion.
The power is external, supplied through, say, a hundred-metre length of stout cable spooling out from a horizontal drum. This cable doubles as a retrieval mechanism.
Use:
Thirty-odd pairs of these are positioned stealthily in the dark, at intervals of about ten metres in line abreast. (Handling the cable-reels and power supplies in these circumstances will require practice).
At staggered intervals, they start to walk across the minefield.
From the trench opposite, what you hear is a faint rustling sound and the occasional explosion of an anti-personnel mine. It sounds as if an enemy platoon is sneaking up on you but, when you fire in their general direction, there's nothing there.
Nothing and no-one reaches the trench opposite. Eventually, its occupants try to get some sleep.
However, the next morning, there are multiple safe-ish paths through the minefield. If, because of the time of year or the location, the ground is soft, they are even marked out by big distinctive boot prints into which real advancing soldiers can safely put their feet.
Of course, you wouldn't have to *use* these paths in every case; you could just go up and down the line, depriving the other side of sleep and keeping them guessing.