if you can just "slide" the old gasket out, then yeah sure, just slide the new one in.
the surfaces would have to be clean for the old one to just slide out.
I personally have never even heard of an oil pan gasket that just slid right off. They usually took a little scraping and picking and all of that to get them off.
So, to pull the oil pan off/out, you have to at the very least, raise the engine.