The phrase "slant upward" is correct and can be used in written English.
It is often used to describe an upward slope or incline. Example: The road ahead began to slant upward, leading us to the top of the mountain.
Isotherms will slant upward toward the shore, and hypolimnion water may even become exposed at the surface.
A few feet away, offering the occasional opinion about a necklace or a pair of earrings, was Amanda Harlech, a lithe, forty-seven-year-old with black hair and green eyes that slant upward.
The slabs down the central corridors have settled in such a way that they slant upward, which is fortunate, because whenever the building's plumbing gives out, the floor acts as a gully, channeling water away from the cells.
Since the beams slant upward, the eye looks upward, as well, causing the eye to perceive a taller space.
The Pritchard Cheval mirror (£167) is slanted upward to maximise that illusory space.
He thought in the moonlight of the things he knew about her: the jewelled navel, the thin face and high cheekbones, the gray eyes that slanted upward at the corners, and her long stride for a girl.
However, the long-term trend -- even in recent years -- has stuck close to a straight line, slanting upward, except for one big dip representing the great depression of the 1930s.
It was built on an old industrial site as part of a larger effort to reclaim a stretch of ruined waterfront, and, despite its unpromising location, its roof — which slants upward from the harbor and seems to emerge from the water — has become a busy public square.
Third, for the stage, he started with a Roman acting platform, but instead of the scaenae frons, he introduced a raked platform, slanted upward toward the rear, on which the perspective setting of a street was made up of painted canvases and three-dimensional houses.
A speed trap sits before a long sweeping right-hander; creep past, then downshift, leaning into the throttle as the road slants upward and the engine crescendos from whuffling complacency to high-pitched eagerness.
Results showed that when an aquifer layer with a low K overlies a layer with a relatively high K, slanting upward flow of diluted saltwater and re-circulated seawater flow are refracted at the interface between the two layers, resulting in streamline separation and a broad mixing zone in the low-K layer.
