
Ah all is clear now at this age you do need three hands if you intending to show her stacked ;)
Irrespective how you are training her(ie walking her into a 4 square stance or placing her into same)it might be easier if you train a stand stay so that she understands the stay word separately from the show stance so that when she is in the right position you can get her to stay there
A little & often & once she gets it right don't repeat it, this way she will remember(hopefully)the last thing you trained
If you are doing training at home walking into the stand might be easier & as soon as she is stood almost or competely 4 square treat her If she has learnt the stay command she should(in theory anyway;) )stay & allow you to do minor adjustments in her legs. having a totally free standing breed in cavaliers I teach a stay stand for the end of the individual & a "show stand"for when we are in with the other dogs