To do the Frog Stretch, kneel on the ground and spread your knees as wide as possible while also supporting yourself on your forearms.
Turn your toes out as you open your knees as wide as possible and lay the inside of your feet against the ground. Do not let your heels come together behind your butt. You want your feet wide apart so that your ankles are in line with your knees if possible.
Bringing your heels together reduces the stretch.
Then sit your butt back toward your heels as much as possible while keeping your knees wide. You may not be able to sit back much, but just push back as far as you can. Feel a nice stretch in your inner thighs and even around the back of your legs.
Breathe as you sit back and feel the stretch. Hold for a second or two and then release out of the stretch, coming back forward for a second before pressing your butt back as far as you can toward your heels again.
As you rock back and forth, you can also work to open your knees up further.