Papaver is the name (genus) for all the poppy family, so it depends on which variety your friends had. Was it papaver somniferum (opium poppy) for example, or papaver orientale (oriental poppy) or Iceland poppies (p.nudicaule)?
Some are biennial, some perennial, some annual. Sowing in the height of summer is unlikely to be successful as they won't germinate if conditions are dry and for biennial types sowing in the autumn would be better. The annual and biennial types don't transplant easily so would be better sown directly in the soil.
Personally I'd recommend sowing them all in spring when the soil has warmed up.
I've never raised the perennial Papaver Orientale from seed but I'd guess this would be better done in a seed tray or a pot.