You can use BasicTextField, it’s a plain text field without any decorations. Note that it doesn’t have placeholder/hint too, you have to implement those by yourself if you need.
BasicTextField(value = "", onValueChange = {}, Modifier.fillMaxWidth())
Since 1.2.0-alpha04 it’s much easier to make your BasicTextField look like TextField or OutlinedTextField. You can copy source code of TextField, which is pretty short since most of logic was moved into TextFieldDefaults.TextFieldDecorationBox, and pass the needed padding value into contentPadding parameter of TextFieldDefaults.TextFieldDecorationBox.