There are gel-like resins, but you'd have massive issues with air entrapment. There's really no shortcut for making these. Casting in layers is the most common approach, but as noted in the article, it's hard to avoid slight refractive index discontinuities.
If it's fluid, I guess you always would have an issue with buoyancy/density. The things you want to suspend will either want to float up or sink down before it cures.
But maybe it could work with something like beads of same refraction index, and then pour resin in when everything is in place? At least it works for water, I've seen it used for decorations and then pouring water over when everything is in place.
Random video showing what I mean: https://www.youtube.com/shorts/LuTlY6DkHQw
I don't know how viscous SLA 3D printer resin is, but if it could be made viscous enough then it seems like maybe you could just suspend the parts in it, tweaking their positions as much as you want until they're just right, then blast the whole thing with enough UV to cure all of it.