When running towards an activated portal that is built 1 block above ground level and then jumping to land half block before the structure base, the player crosses the portal. To reproduce the bug, first a nether portal needs to be built like in the image previously provided, then, when running towards the portal, after jumping so that the player lands near the base blocks, then continuing running, if done correctly, the player will cross the portal without being on the blocks where the portal is activated