Direct answer: Cleaning a dirty oven can be done effectively with common household supplies and a few safety steps. Below is a practical, step-by-step approach you can follow. Step-by-step guide

• Safety first: Unplug the oven if possible and ensure the area is well ventilated by opening a window or turning on the range hood. Wear gloves and eye protection to protect skin and eyes from cleaners and splashes.
• Remove everything: Take out all racks, trays, and any utensils from the oven. Soak racks separately in hot, soapy water or a vinegar-water solution.
• Choose a cleaning method:
  • Overnight baking soda paste (best for heavy buildup):
    • In a bowl, mix baking soda with a small amount of water to form a thick paste.
    • Spread the paste all over the interior surfaces of the oven, avoiding heating elements and any electrical components.
    • Let it sit overnight (8–12 hours). This softens grease and carbonized residue.
  • Quick steam method for lighter grime:
    • Place a shallow, heat-safe dish with water and a few tablespoons of white vinegar inside the oven.
    • Heat at 200°F–250°F (90°C–120°C) for about 15–20 minutes to create steam that loosens grime.
• Scrub and wipe:
  • After the paste has set (or once steam has loosened grime), use a non-abrasive sponge or nylon scrubber to wipe away loosened residue.
  • For stubborn spots, reapply a small amount of paste or cleaner and scrub again, then wipe clean with a damp cloth.
  • Use a plastic or silicone spatula to lift off hard crusts without scratching.
• Rinse and dry:
  • Wipe all interior surfaces with a damp cloth to remove any remaining residue.
  • Dry with a clean towel. Return the racks after drying.
• Optional finishing touches:
  • For a fresh scent and extra shine, wipe with a cloth dampened with a mixture of equal parts water and white vinegar, then dry.
  • If you use a commercial oven cleaner, follow the product instructions precisely and ensure thorough rinsing with a damp cloth to remove chemical residues.

Alternative natural methods

• Lemon steam: Cut a lemon in half, place in an oven-safe dish with water, and heat to produce steam that loosens grease. Wipe down after cooling.
• Vinegar and baking soda combo: Apply a baking soda paste to tough spots, mist with white vinegar to fizz and loosen grime, then scrub and wipe clean.

Racks and trays

• Soak heavily soiled racks in hot water with a few drops of dish soap or a bit of dishwasher tablet dissolved in hot water for 1–2 hours, then scrub with a non-abrasive pad and rinse thoroughly.
• For chrome racks, avoiding harsh abrasives helps prevent scratching.

Tips to prevent future buildup

• Wipe spills promptly after cooking to reduce baked-on residues.
• Place a sheet of aluminum foil or a shallow pan on the bottom rack to catch drips when roasting.
• Clean on a regular schedule (monthly or biweekly) to keep grime manageable.

What to avoid

• Do not spray cleaning products directly onto heating elements or electrical components.
• Avoid highly abrasive pads that can scratch enamel.
• Do not mix bleach with ammonia or acidic cleaners—this can release dangerous gases.

If you’d like, tell me your oven type (self-cleaning, conventional electric, gas, etc.) and the severity of the buildup, and I can tailor the method and timings more precisely.