Hi...

I use liners in my electric fan oven, but not on the bottom, I have one on
each shelf, when the cooking time is up, I pull it out **with** whatever
is in the oven, so that it is like a tray for the main dish, then spills
don't get on the bottom of the oven.

If you have to leave it behind in the oven because your 'dish' is heavy,
then just go real careful if the contents are liquidy... and wipe any spills
up as soon as the meal is over, scrape it up if it has gone a bit tacky with
a wooden spatula, or similar. I know it's a horrid fussy messy job, but
it'll save you lots of sweat and tears, and certainly lots of drill bits
(g).
I do however put foil into the bottom of the grill pan under the wire or
metal trivet thingy..

HTH....Cher