There are two elements to front-splits: The hamstrings and the hips. Both will need stretching to accomplish what you want. You'll also need to strengthen the surrounding musculature, or you'll be stretchy but not strong enough to safely get into and out of the position(s) you want. The length of time it'll take you to achieve this will depend on your body, so please be aware of your limits and don't push too hard. As always, having a trainer assess your body and what it needs specifically is the best way to reach a difficult goal, but if you're generally fit and flexible, this should work for you:
First, add squats to your workout, if they aren't there already. Focus on spreading your legs wide (knees point outward more than forward), and on dipping and raising smoothly. Keep your back straight (butt under, not sticking out) and your heels on the floor. This will build the hip and leg strength you need. The squat with the widest stance is called sumo squat, example here.
After your regular stretching, place a pillow or yoga-block in front of you, put your hands on it, and sink down into a forward split as far as you can. Stay static and hold this posture for one full minute. Try to RELAX your hip and leg-muscles, and let yourself sink further if you can, but don't "push" downwards. (Trust me, this will hurt enough without pushing.) You'll feel this mostly in your hamstrings.
Get up, shake it out, and turn to the side. Do a deep lunge with your rear leg straight and the front leg bent. Your knee should NOT be farther forward than your toe, however -- this is very important. Make sure your rear leg stays perfectly straight. Focus on keeping your upper body vertical -- even bent slightly backwards is ok if it helps you stretch -- and letting your weight sink into your forward hip as far as possible. (This is basically a side split, but stabilized by your front foot for safety. Once you can do a side-split, it's safe to do this hip stretch by just doing the split, with your body vertical and focusing on sinking into the hip, same as described here.) This is to stretch your hip-flexor and tendons; again, breathe, and try to relax your quads (thigh-muscles) and stomach, letting your body-weight pull you farther into the stretch. If you're comfortable, it's safe to add a gentle dynamic stretch to this -- a few small "bounces" -- to encourage it to sink farther.
Do the same side-split stretch on the other side.
It's safe to do these stretches daily, but listen to your body and take a day off (do gentler stretches on that day, so you don't get stiff) if you become way too sore or feel unstable. Make sure you're drinking LOTS of water during flexibility training!
(Source: My personal trainer in martial arts, and his sifu, both use this training sequence for teaching splits to kungfu students (including me). While some may argue that the dynamic and strength-building components are only necessary for jumping and kicking, we would disagree; training flexibility without strength is a recipe for future injury, which is why these exercises are all isometric and include muscle-strengthening companion exercises like squats. We also deliberately don't train JUST hamstring flexibility, since it's easy to injure yourself if your legs are very flexible but your hips are not.)