Place the flour in a shallow bowl and season with salt and pepper. Heat a large saute pan over medium-high heat, then add the oil. Dredge the chicken in the flour, shaking off any excess, and place in the hot oil. Cook until golden brown on both sides and cooked through, about 4 minutes per side. Remove the chicken to a plate.
Add the garlic to the pan, carefully add the wine and, using a wooden spoon, scrape the bottom of the pan to release any flavor stuck to the bottom. Add the cream, Parmesan, lemon zest and juice and some salt and pepper. Bring to a simmer and cook until the sauce starts to thicken, about 2 minutes. Add the spinach, stir and return the chicken to the pan. Cook for 1 minute more, until the spinach has wilted. Garnish with basil and lemon slices.
Make sure to fully cook the chicken thighs when searing; if they still need to cook at the end, the spinach will get ugly.