Warm the tortillas before adding the filling - you can do this by wrapping in kitchen paper and placing in the microwave for a few seconds, but the best was is to warm a dry skillet/frying pan over a medium head and cook for place a tortilla in for around 30 seconds each side (or more/less until just warm rather than crisp). I tend to warm one, start filling, and have another warming as I work to then fill next.
Place some chicken in a line towards one side of the warmed tortilla then roll it up - you want it relatively snug so the chicken stays in, but bear in mind the tortilla will swell up a little as it cooks, so don't try to make it too tight or it will burst. Secure the tortilla closed by placing a cocktail stick through the rolled tortilla right through the middle (see photos above/video).
Repeat with the rest of the tortillas and chicken, and get your toppings ready - shred lettuce, make pico de gallo if not already made, crumble cheese.
Warm some oil over a medium-high heat in a skillet/frying pan that is just a little wider than the tortillas are long so a few can cook in at once, but without too much extra space. You want probably around ⅔in (2cm) depth of oil, so that it will come around halfway up the tortillas as they cook.
Once the oil is warm, add a few flautas to the skillet. You don't want to over-crowd the pan and remember you need a little space for turning so leave a little space between them. Cook, turning now and then, for a few minutes until they are crisp outside (you can make them more or less crispy to taste).
Carefully remove the cooked flautas from the pan, tip to one side to let any oil stuck inside drain out then place on kitchen paper to drain further before serving. Repeat cooking the rest of the flautas.
Once ready to serve, top the flautas with the shredded lettuce, crema, cheese and pico de gallo (traditionally added in that order). You would typically stack them all together and top, though if easier, you can do on separate plates for individual servings.