I have the feeling the answer to this will come down to ''impossible'' but let's ask anyway to be sure.
We know gas Giants have no solid surface and if you tried to land on one you would fall into the planet till you reach the solid core (at wich point you would have most likely been crushed into oblivion by pressure)
But i know gas can freeze if it gets cold enough (even thought i heard something about gas under right conditions being able to freeze/solidify so fast it skips the ''liquid'' state entirely and goes straight from gas to solid)
Now suppose you have a gas giant orbiting at a very extreme distance from it's parent star so it would recieve nearly no warmth from it, or go even further and make it a rogue planet without a star. Could the ''surface'' (for lack of a better word) of such a hypothetical gas giant become cold enough for it to freeze/solidify into a solid surface one could stand on? (preferrably while the lower layers of the planet under the frozen layer remain gaseous)
Below this paragraph i will add a picture showing on the left a cross section of a ''typical'' gas giant (using Jupiter as a basis) and on the right my hypothetical ''frozen'' gas giant.