The most important thing is to be consistent with whatever method you choose!

Taking her out a few minutes after she eats, then praising her when she does something outside are good. Stay out until she does something! You need to watch her very carefully inside, too - and if she starts to "squat" (I know, a little hard to tell on a Corgi ...) quick - say "NO!" and rush her outside! Then praise again when she "does her business" outside.

Time, patience and consistency are the keys!