pack -side -anchor

set f1 [frame .f1 -bg green]

set l1 [label $f1.l1 -text Label-1 -bg red]
set l2 [label $f1.l2 -text Label-2 -bg red]

pack $f1 -fill both -expand true
pack $l1 -side top -anchor nw
pack $l2 -side top -anchor se

set f2 [frame .f2 -bg blue]

set l3 [label $f2.l3 -text Label-3 -bg red]
set l4 [label $f2.l4 -text Label-4 -bg red]

pack $f2 -fill both -expand true
pack $l3 -side left -anchor nw
pack $l4 -side left -anchor se