One of the key advantages of van der Waals materials is the great flexibility in materials engineering, giving rise to the unprecedented possibility of realizing multifarious quantum phases. This talk will be focused on two examples ( in 1D and 2D, respectively) from our recent work in this aspect. The first one is the discovery of 1D single-unit-cell-width CrCl₃ atomic wires. Such a 1D wire, consisting of a single row of face-sharing CrCl₆ octahedra, was grown solely on an isotropic NbSe₂ vdW surface. Scanning tunneling microscopy/spectroscopy and first-principles calculations jointly revealed that the single wire is a large-gap semiconductor exhibiting a Néel-type antiferromagnetic coupling. The underlying growth mechanism reveals the critical importance of the vdW interface interaction in controlling the dimensionality conversion. The second example reports a highly controllable and scalable conversion of a monolayer nonmagnetic semiconductor into a correlated magnet. Specifically, we revealed multiple kagome flat bands across the Fermi level in monolayer MoTe_2-x by fabricating a uniformly ordered mirror-twin boundary superlattice (corresponding to a stoichiometry of MoTe_56/33). The partial filling nature of flat bands yields a correlated insulating state with spontaneous magnetization.