as wot Fossy said or alternatively. Get an old cheapo second hand seat post to out in the frame to clamp to.
+1I use a Tacx Spider Team & very nice it is too.
I have a stand where the bike rests on the BB shell, cable adjustment is no problem as the guide keeps them clear of the stand.Just thinking about it, there's 1 flaw with that type of stand. You can only adjust gear indexing on the bench if the cables are top-tube or internally routed as the bike rests on the BB shell.
what I find is there's enough cable/resting block interaction to knock the indexing out a touch. You get it perfect on the stand & then it's not quite right on the road.I have a stand where the bike rests on the BB shell, cable adjustment is no problem as the guide keeps them clear of the stand.