There are a lot of FE models out there, some do struggle with that question but not all. For one, there's a model where the Earth is a two-sided disc (there is an explanation for that, but it takes a while to explain, so sustain your disbelief as far as this question goes) so as there are two distinct poles, day lengths are much easier to explain. It's just a matter of where the Sun shines (technically where the Earth tilts, the Sun's not easy to explain under this model either, but you can see how it could work).
Gist: there are models beyond the flat disc with the North Pole at the centre and the South at the rim.
ok, im thinking about it and i can see how the sun could spiral, rather than just circle like in most of the images ive seen. the sun could make a tighter circle in the northern summer, then a wider circle in the northern winter.
am i on track here?
That's how it works in the normal model, though as far as day lengths go, as you pointed out, it doesn't help. With farther to go on the outer track, day lengths would be off.
Under this particular FE model (nicknamed DET, Dual Earth Theory, to help distinguish) the exact means the Sun works are, like I said, pretty complex. The gist is that the Sun in the sky is a projection/reflection, and there are two such projections, one for the North and one for the South. It's simpler than it sounds, I swear, but the details of the mechanism would take a while to go into.
The projections are connected, so as one moves inwards, the other moves outwards, similar to what you said. However, the existence of two poles, one on each side of the disc, mean you'd get what we observe.