First, define the verbs
yacer | to lie
yesar | to plaster
Second, relate them with something
yacer | lecho
yesar | pared
Third, use them in a sentence
Había yacido en el lecho durante horas antes de levantarme. | I had lain in bed for hours before getting up.
Había yesado la pared antes de darme cuenta de que había un agujero. | I had plastered the wall before realizing there was a hole.