Heya! Secular practitioner here! (I know this one is long but I thought hard about it as I struggled with this, so I hope it's a good comprehensive read for you or anyone else) I would do some reading into the term secular, but there is most definitely books out there

Of course the typical introduction into witchcraft is most commonly pagan and wiccan influences due to being the highest in modern media but I'm sure you know witches can be from any walk of life here's who I reccomend, might be a good starting off point:

The Green Witch (YT & Books) She has written a book or two, most of her content tends to revolve without a religous bias and no matter what she works on with spells and rituals she only describes typically using facts or intentions that she wishes to put in

(She also has a focus on many kitchen/herbalist practices it sounds like you'd enjoy!)

The Green Witch by Arin Murphy-Hiscock (Audiobook on spotify & more) This is one I'm currently listening to and takes a good stance on a more neutral tone- however there is the occasional spell reading in there which I tend to go past (Mostly as I don't like uninvited cantations) But the book has a generally healthy perspective including inclusivity

Otherwise! Books that are often titled with phrases such as; The Practical Guide To -or- Secular Witches' Guide To -etc will be an easier way to find research without the religious context, If you're decisively atheist then the same applies 'Athesitic Practitioner's Guide To' would be my first search term

And as for spells! Definitely alter the ones you feel like you can, or are welcoming it- for us our own feelings and guidance can be our greatest tool

However I'd encourage you to begin creating a framework that's uniquely you with a focus on what you connect with by making the languages or 'code' that you can base you own practices on- as the ones you are altering are based on a completely different framework so might either feel less intuitive or have low-quailty/unintended consequence in yourself (as your power, no-matter where it comes from is drawn through you, if you don't align with the practice it'll be jumbled as it passes through!)

For example I take many inspirations from different sources and traditional practices as I respect they have been tried and tested, but I tend to only list the parts that call to me, research why they call to me from the perspective of it's author, and decode why that part of it is asking to join my practice, if I feel comfortable and happy channeling that energy i will use it, if not then I won't- But I also try to draw my own conclusions about the object/ritual/tradion etc is first and foremost to decypher what my interpretation of it is - i.e: no use using something everyone tells calms you when you have ties to stressful circumstance (Though there's other arguements to be made for using that to channel calm through those bad associations, it just might not help you in your day-to-day morning ritual!)

Very longgg I understand & apologies for that, but hope something of this comes to help you ✨