Can you be more specific and tell us which oak, aster?

Baptisia seed sown freshly harvested germinates almost immediately. Older seed that has been dried and stored is slow to sprout. Pour very hot water over stored seed and allow it to cool and soak for a couple of days. Germination may be more than two weeks so be patient.

Very few aster need a cold moist period or any kind of conditioning before they will germinate and you should be fine sowing those indoors.

Oak on the other hand (Quercus) with only a couple of exceptions will benefit from experiencing a wide range of fluctuating temperatures before being brought to warmer to germinate. Fall sowing outdoors is often best. Some will require a warm moist period before an extended moist chill, others are fine with the moist chill of several weeks only. So, which oak?

Black Oak, Scarlet Oak, New England Aster, Showy Aster

New England Aster (asternovae-angliae), Sow at 68F, germination slow - you could start these now. Showy Aster (aster spectabilis) will germinate more reliably if you can give it a moist cold period of 6 weeks, then should germinate in 2-3 weeks once brought back to warm.

Black oak can mean more than one tree. Going by your zone, maybe Eastern Black Oak?Quercus velutina - "Seed can quickly lose viability if allowed to dry and if stored, is best sown fresh in Fall outdoors." You could try giving them 2 months moist chill of 35-40F then bringing back to warm. Suggestions are approximately the same for Scarlet Oak ( quercus coccinea). Fall sowing best and may be better than artificial stratification (the cold moist period). Since its too late to Fall sow, you'd have nothing to lose by trying. Consider soaking overnight before providing the moist chill period.