best way in cold is 12 inch insulated footer for foundation stainless steel venting ( for bales water ingress from melting and to stop rodents)…if you have the $$ do a steel i beam frame… if you want fast then go container home.instead.
dont do plaster do spray concrete with fiberglass or elastic polymers it last longer and you can have the colour impregnated
make sure you do a slanted roof metal is best tile is too heavy will cause walls to fail.
do it when dry or you have problems remember wet straw bales can spontaneously combustion.
check all bales for moisture content wet stuff is garbage.
there are lots more things about bale houses for northern wet climates with snow better for dryer arid places